It seems this is a known issue discussed on the Empower KB article…Check this out:
If you have no immediate access to the site here is the direct info:
There is an UncaughtExceptionHandler in queue ‘ServiceAssoc Queue’ error occurrence in server log.
Please check why the error occurs. Why the error “UncaughtExceptionHandler in queue ‘ServiceAssoc Queue’” occurs in server log (but no error in Error log).
Integration Server (IS) is clustered and there is no interface problem. This error occurs irregularly after we have upgraded and went live.
In IS admin page > Setting> Logging, the mode of Service logger is set by Asynchronous, Guaranteed is set by No and Destination is set by File.
There was a similar issue when a service that closes sessions on Lotus Domino servers. It seems like there was a new java service implemented in the environment to search the staff number and do substring it. It is communicating with Domino Notes and then searching staff number. There was a similar issue when a service that closes sessions on Lotus Domino servers using the Domino Java API (NCSO.jar).
The mentioned java service looks like generating those errors - “UncaughtExceptionHandler in queue 'ServiceAssoc Queue”. It is a service that closes sessions on Lotus Domino servers using the Domino Java API (NCSO.jar). It should close the session correctly but generates those errors.
If this is the case, do try to install a newer version of the Lotus Domino Java API (NCSO.jar). Also, make sure the jar files you’re compiling against match the version you’re running with. You may engage your vendor regarding this as the third party solution.
The issue is resolved after mentioned API driver version upgrade.