Checkmk 2.1.0: EventConsole "Generate Event" button causes "Internal Server Error" message

CMK Version: 2.1.0p2, 2.1.0p3, 2.1.0p4 CEE

OS version: SLES12 SP5

Error description: When trying to create a event (snmptrap) out of the Event Console with “Generate Event” button a “Internal Server Error” is shown

Error message (GUI): "Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at nobody@localhost to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log."

Error message (/var/log/apache2/access_log):
xxxx - - [29/Jun/2022:21:35:20 +0200] “GET /xxx/check_mk/ HTTP/1.1” 500 529