A few hypervisors on the Paris zone had a configuration issue between 12:21 UTC and 14:16 UTC leading to instances not being properly monitored. This caused Monitoring/Unreachable deployments for the instances hosted on them.
Because of this, those hypervisors became more empty than the others. More VMs were scheduled on them since they had more resources available, which then lead to more Monitoring/Unreachable events.
Instances weren't, for the most part, unreachable, but were redeployed anyway.
This should now be fixed. Sorry for the inconvenience