I seem to have a similar problem.
Running a Debian server which I upgraded from 9 to 11 recently. Since then I have issues with ZM. I realised that 1.36 is now the current version so I changed the zoneminder.list file to point to 1.36 bullseye.
But now it seems to be completely broken. Not sure where to start with to be honest. Here some recent messages from the logfile:
"2022-04-19 10:22:11",zmdc,,272483,INF,"'zmc -m 3' crashed, signal 6",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,272483,INF,"'zmc -m 2' starting at 22/04/19 10:22:10, pid = 288997",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,288997,INF,"'zmc -m 2' started at 22/04/19 10:22:10",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,272483,INF,"Starting pending process, zmc -m 2",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,288995,INF,"'zmc -m 3' started at 22/04/19 10:22:10",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,272483,INF,"'zmc -m 3' starting at 22/04/19 10:22:10, pid = 288995",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,272483,WAR,"!send_stop so starting 'zmc -m 3'",zmdc.pl,'-
"2022-04-19 10:22:10",zmdc,,272483,INF,"Command 'zmc -m 3' removed from pending list at 22/04/19 10:22:10",zmdc.pl,'-
"2022-04-19 10:22:10",zmwatch,,272552,INF,"Restarting capture daemon for Atrium, shared data not valid",zmwatch.pl,'-
"2022-04-19 10:22:10",zmdc,,272483,INF,"'zmc -m 2' crashed, signal 6",zmdc.pl,'-
"2022-04-19 10:22:10",zmwatch,,272552,ERR,"Memory map file '/dev/shm/zm.mmap.3' does not exist in zmMemAttach. zmc might not be running.",zmwatch.pl,'-
"2022-04-19 10:22:09",zmdc,,272483,INF,"'zmc -m 2' starting at 22/04/19 10:22:09, pid = 288989",zmdc.pl,'-
"2022-04-19 10:22:09",zmdc,,288989,INF,"'zmc -m 2' started at 22/04/19 10:22:09",zmdc.pl,'-
"2022-04-19 10:22:09",zmdc,,272483,WAR,"!send_stop so starting 'zmc -m 2'",zmdc.pl,'-
"2022-04-19 10:22:09",zmdc,,272483,INF,"Command 'zmc -m 2' removed from pending list at 22/04/19 10:22:09",zmdc.pl,'-
"2022-04-19 10:22:09",zmwatch,,272552,INF,"Restarting capture daemon for Kreuzgasse, shared data not valid",zmwatch.pl,'-
"2022-04-19 10:22:09",zmwatch,,272552,ERR,"Memory map file '/dev/shm/zm.mmap.2' does not exist in zmMemAttach. zmc might not be running.",zmwatch.pl,'-
"2022-04-19 10:22:06",zmdc,,272483,INF,"'zmc -m 3' crashed, signal 6",zmdc.pl,'-
"2022-04-19 10:22:05",zmdc,,272483,INF,"'zmc -m 3' starting at 22/04/19 10:22:05, pid = 288976",zmdc.pl,'-
"2022-04-19 10:22:05",zmdc,,288976,INF,"'zmc -m 3' started at 22/04/19 10:22:05",zmdc.pl,'-
"2022-04-19 10:22:05",zmdc,,272483,INF,"Starting pending process, zmc -m 3",zmdc.pl,'-
"2022-04-19 10:22:04",zmdc,,272483,INF,"'zmc -m 2' crashed, signal 6",zmdc.pl,'-
"2022-04-19 10:22:04",zmdc,,288973,INF,"'zmc -m 2' started at 22/04/19 10:22:04",zmdc.pl,'-
"2022-04-19 10:22:04",zmdc,,272483,INF,"'zmc -m 2' starting at 22/04/19 10:22:04, pid = 288973",zmdc.pl,'-
"2022-04-19 10:22:04",zmdc,,272483,INF,"Starting pending process, zmc -m 2",zmdc.pl,'-
"2022-04-19 10:22:01",zmdc,,272483,INF,"'zmc -m 3' crashed, signal 6",zmdc.pl,'-
"2022-04-19 10:22:00",zmdc,,272483,INF,"'zmc -m 2' crashed, signal 6",zmdc.pl,'-
"2022-04-19 10:22:00",zmdc,,288965,INF,"'zmc -m 3' started at 22/04/19 10:22:00",zmdc.pl,'-
"2022-04-19 10:22:00",zmdc,,272483,INF,"'zmc -m 3' starting at 22/04/19 10:22:00, pid = 288965",zmdc.pl,'-
Let me know what I can provide to enable you to help me.