Here's the SQL exception from the stack trace.
Caused by: java.sql.SQLException: Unique constraint violation: in statement [insert into TIMERS TIMERID, TARGETID, INITIALDATE, TIMERINTERVAL, INSTANCEPK, INFO) values (?,?,?,?,?,?)] at org.hsqldb.jdbc.Util.throwError(Unknown Source) at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)
It's an ongoing issue for which I've been unable to get an answer here for also. The best thing you can do is go into the HSQL database manager through the JMX console and delete all timers before re-deploying your app.