Monitors randomly stop working - monitors locked but never unlocked?

**Describe the bug**
Monitors randomly break causing them to not alert anymore on incidents. I also cannot get them back to work without removing them and re-adding them. Then they work for a while again, but end up breaking again after a while.

I have read some other (closed) issues suggesting persistence issues, but this is not the case here:
- I only have Checkmate running on 1 dedicated machine
- The database is a bind-mount to the file system, so not a volume:
``` - /docker_compose/checkmate/mongo/data:/data/db ```
- The server has not been down or turned off

**To Reproduce**
I cannot reproduce it at will.

**Expected behavior**
I expect the monitors to keep running and be fault-tolerant

**Screenshots**

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**Additional context**
From the Job queue, it seems like the entries for these monitors are locked, but never unlocked. See screenshot.

The issue provides no file or test entry point; begin by tracing the Job queue entries for affected monitors and the monitor lock/unlock lifecycle. Reproduce or inspect the locked state if possible, and consider the issue done only when monitors continue alerting without removal and re-addition and queue locks are released.

Written by the indexing model from the issue text.