running out of memory is the main cause of php crashing with no error handling. Maybe turning debug off gave you a little more headroom, but the issue might still be lurking there just waiting for you to add some more complexity,

I remember it was working fine before. Then at some point I updated WAMP and didn't notice it first because at that time I wasn't working on jobs on the Windows 11 machine. Only later at some point I noticed it when adding features to a job and testing them that no exception was thrown and PHP quit silently. As mentioned in the OP it already failed silently when forcing a simple exception like division by zero. So I think it wasn't an out of memory issue. Also the same (faulty) code produced an exception output and log on a different machine (Mac).

If anyone stumbles upon this thread because they have the same issue, I finally found the cause:

Installing WAMP enabled the xdebug extension in the php.ini and that caused the issue. Setting xdebug.mode=off and restarting the WAMP services fixed the problem.