We identified the cause of the issue, caused by a failure in the behavior of our orchestration framework that happens in some very specific situations.
The fix for this issue will be deployed in production on Thursday 26th of February.
We've also clarified the impact of the incident: only one of the tenants of the cell is impacted, and only 7 scheduled monitors of this tenant are impacted (meaning they are no longer running according to their schedules). The customer associated with this tenant has already been contacted by our team.