I am fairly new to wildfly and I barly have any experience with Ubuntu. I have tried to install wildfly in version 16.0.0.Final onto Ubuntu 18.04 LTS using the instructions given by Install and Configure Wildfly (JBoss) on Ubuntu 18.04 LTS . It all worked fine on a local Ubuntu which I installed on virtual box. But when I try to install it on a rented server I'll get a java.util.concurrent.RejectedExecutionException.
Does anyone has an idea what went wrong?
When I enter the command sudo systemctl status wildfly I'll get the following message:

● wildfly.service - The WildFly Application Server

   Loaded: loaded (/etc/systemd/system/wildfly.service; disabled; vendor preset: enabled)

   Active: failed (Result: exit-code) since Wed 2019-07-24 16:50:25 CEST; 19min ago

  Process: 8351 ExecStart=/opt/wildfly/bin/launch.sh $WILDFLY_MODE $WILDFLY_CONFIG $WILDFLY_BIND (code=exited, status=1/FAILURE)

Main PID: 8351 (code=exited, status=1/FAILURE)

Jul 24 16:50:22 h2830632.stratoserver.net systemd[1]: Started The WildFly Application Server.

Jul 24 16:50:25 h2830632.stratoserver.net systemd[1]: wildfly.service: Main process exited, code=exited, status=1/FAILURE

Jul 24 16:50:25 h2830632.stratoserver.net systemd[1]: wildfly.service: Failed with result 'exit-code'.

I then tried to make any sense of the server log with cat /opt/wildfly-16.0.0.Final/standalone/log/server.log

2019-07-24 16:50:23,357 INFO  [org.jboss.modules] (main) JBoss Modules version 1.9.0.Final

2019-07-24 16:50:24,056 WARN  [org.jboss.as.server] (main) WFLYSRV0266: Server home is set to '/opt/wildfly/standalone', but server real home is '/opt/wildfly-16.0.0.Final/standalone' - unpredictable results may occur.

2019-07-24 16:50:24,090 INFO  [org.jboss.msc] (main) JBoss MSC version 1.4.5.Final

2019-07-24 16:50:24,097 INFO  [org.jboss.threads] (main) JBoss Threads version 2.3.3.Final

2019-07-24 16:50:24,313 INFO  [org.jboss.as] (MSC service thread 1-1) WFLYSRV0049: WildFly Full 16.0.0.Final (WildFly Core 8.0.0.Final) starting

2019-07-24 16:50:24,315 DEBUG [org.jboss.as.config] (MSC service thread 1-1) Configured system properties:

        [Standalone] =

        awt.toolkit = sun.awt.X11.XToolkit

        file.encoding = UTF-8

        file.separator = /

        java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment

        java.awt.headless = true

        java.awt.printerjob = sun.print.PSPrinterJob

        java.class.path = /opt/wildfly/jboss-modules.jar

        java.class.version = 55.0

        java.home = /usr/lib/jvm/java-11-openjdk-amd64

        java.io.tmpdir = /tmp

        java.library.path = /usr/java/packages/lib:/usr/lib/x86_64-linux-gnu/jni:/lib/x86_64-linux-gnu:/usr/lib/x86_64-linux-gnu:/usr/lib/jni:/lib:/usr/lib

        java.net.preferIPv4Stack = true

        java.runtime.name = OpenJDK Runtime Environment

        java.runtime.version = 11.0.3+7-Ubuntu-1ubuntu218.04.1

        java.specification.name = Java Platform API Specification

        java.specification.vendor = Oracle Corporation

        java.specification.version = 11

        java.util.logging.manager = org.jboss.logmanager.LogManager

        java.vendor = Oracle Corporation

        java.vendor.url = http://java.oracle.com/

        java.vendor.url.bug = http://bugreport.java.com/bugreport/

        java.version = 11.0.3

        java.version.date = 2019-04-16

        java.vm.compressedOopsMode = 32-bit

        java.vm.info = mixed mode, sharing

        java.vm.name = OpenJDK 64-Bit Server VM

        java.vm.specification.name = Java Virtual Machine Specification

        java.vm.specification.vendor = Oracle Corporation

        java.vm.specification.version = 11

        java.vm.vendor = Oracle Corporation

        java.vm.version = 11.0.3+7-Ubuntu-1ubuntu218.04.1

        javax.management.builder.initial = org.jboss.as.jmx.PluggableMBeanServerBuilder

        jboss.bind.address = 0.0.0.0

        jboss.home.dir = /opt/wildfly

        jboss.host.name = h2830632

        jboss.modules.dir = /opt/wildfly/modules

        jboss.modules.system.pkgs = org.jboss.byteman

        jboss.node.name = h2830632

        jboss.qualified.host.name = h2830632.stratoserver.net

        jboss.server.base.dir = /opt/wildfly-16.0.0.Final/standalone

        jboss.server.config.dir = /opt/wildfly-16.0.0.Final/standalone/configuration

        jboss.server.data.dir = /opt/wildfly-16.0.0.Final/standalone/data

        jboss.server.deploy.dir = /opt/wildfly-16.0.0.Final/standalone/data/content

        jboss.server.log.dir = /opt/wildfly-16.0.0.Final/standalone/log

        jboss.server.name = h2830632

        jboss.server.persist.config = true

        jboss.server.temp.dir = /opt/wildfly-16.0.0.Final/standalone/tmp

        jdk.debug = release

        line.separator =

        logging.configuration = file:/opt/wildfly/standalone/configuration/logging.properties

        module.path = /opt/wildfly/modules

        org.jboss.boot.log.file = /opt/wildfly/standalone/log/server.log

        org.jboss.resolver.warning = true

        os.arch = amd64

        os.name = Linux

        os.version = 4.15.0

        path.separator = :

        sun.arch.data.model = 64

        sun.boot.library.path = /usr/lib/jvm/java-11-openjdk-amd64/lib

        sun.cpu.endian = little

        sun.cpu.isalist =

        sun.io.unicode.encoding = UnicodeLittle

        sun.java.command = /opt/wildfly/jboss-modules.jar -mp /opt/wildfly/modules org.jboss.as.standalone -Djboss.home.dir=/opt/wildfly -Djboss.server.base.dir=/opt/wildfly/standalone -c standalone.xml -b 0.0.0.0

        sun.java.launcher = SUN_STANDARD

        sun.jnu.encoding = UTF-8

        sun.management.compiler = HotSpot 64-Bit Tiered Compilers

        sun.os.patch.level = unknown

        user.country = DE

        user.dir = /

        user.home = /opt/wildfly

        user.language = de

        user.name = wildfly

        user.timezone = Europe/Berlin

2019-07-24 16:50:24,319 DEBUG [org.jboss.as.config] (MSC service thread 1-1) VM Arguments: -D[Standalone] -Xms64m -Xmx512m -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true --add-exports=java.base/sun.nio.ch=ALL-UNNAMED --add-exports=jdk.unsupported/sun.misc=ALL-UNNAMED --add-exports=jdk.unsupported/sun.reflect=ALL-UNNAMED --add-modules=java.se -Dorg.jboss.boot.log.file=/opt/wildfly/standalone/log/server.log -Dlogging.configuration=file:/opt/wildfly/standalone/configuration/logging.properties

2019-07-24 16:50:24,963 ERROR [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0055: Caught exception during boot: org.jboss.as.controller.persistence.ConfigurationPersistenceException: WFLYCTL0085: Failed to parse configuration

        at org.jboss.as.controller@8.0.0.Final//org.jboss.as.controller.persistence.XmlConfigurationPersister.load(XmlConfigurationPersister.java:145)

        at org.jboss.as.server@8.0.0.Final//org.jboss.as.server.ServerService.boot(ServerService.java:385)

        at org.jboss.as.controller@8.0.0.Final//org.jboss.as.controller.AbstractControllerService$1.run(AbstractControllerService.java:374)

        at java.base/java.lang.Thread.run(Thread.java:834)

Caused by: java.util.concurrent.RejectedExecutionException

        at org.jboss.threads@2.3.3.Final//org.jboss.threads.RejectingExecutor.execute(RejectingExecutor.java:37)

        at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor.rejectException(EnhancedQueueExecutor.java:1999)

        at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor.doStartThread(EnhancedQueueExecutor.java:1619)

        at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor.execute(EnhancedQueueExecutor.java:751)

        at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140)

        at org.jboss.as.controller@8.0.0.Final//org.jboss.as.controller.parsing.DeferredExtensionContext.load(DeferredExtensionContext.java:77)

        at org.jboss.as.server@8.0.0.Final//org.jboss.as.server.parsing.StandaloneXml_10.readServerElement(StandaloneXml_10.java:237)

        at org.jboss.as.server@8.0.0.Final//org.jboss.as.server.parsing.StandaloneXml_10.readElement(StandaloneXml_10.java:137)

        at org.jboss.as.server@8.0.0.Final//org.jboss.as.server.parsing.StandaloneXml.readElement(StandaloneXml.java:126)

        at org.jboss.as.server@8.0.0.Final//org.jboss.as.server.parsing.StandaloneXml.readElement(StandaloneXml.java:52)

        at org.jboss.staxmapper@1.3.0.Final//org.jboss.staxmapper.XMLMapperImpl.processNested(XMLMapperImpl.java:122)

        at org.jboss.staxmapper@1.3.0.Final//org.jboss.staxmapper.XMLMapperImpl.parseDocument(XMLMapperImpl.java:76)

        at org.jboss.as.controller@8.0.0.Final//org.jboss.as.controller.persistence.XmlConfigurationPersister.load(XmlConfigurationPersister.java:126)

        ... 3 more

        Suppressed: java.lang.OutOfMemoryError: unable to create native thread: possibly out of memory or process/resource limits reached

                at java.base/java.lang.Thread.start0(Native Method)

                at java.base/java.lang.Thread.start(Thread.java:803)

                at org.jboss.threads@2.3.3.Final//org.jboss.threads.JBossThread.start(JBossThread.java:507)

                at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor.doStartThread(EnhancedQueueExecutor.java:1615)

                ... 13 more

2019-07-24 16:50:25,060 FATAL [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0056: Server boot has failed in an unrecoverable manner; exiting. See previous messages for details.

I anyone knows what could be the problem, I'd be very grateful for feedback.

Thanks

Michael