When the application is tested using selenuim, teiid embeded (teiid is running as a java process to access the backend of the application) process crashed. in the log the java exception was logged
ERROR [NIO0 PROCESSOR]: TEIID40017 Unexpected exception for session yrAdmx5dYAeA java.lang.OutOfMemoryError: unable to create new native thread
You may be hitting a thread limit on your OS. You can use a thread dump to verify that Teiid is creating the expected number of threads. If so, you can either configure the engine and transports to use fewer threads or increase the thread limit for your os.