Over the years, some users reported the presence of inconsistent metadata for the config.system.sessions collection. The most reported issue is the presence of inconsistent collection UUIDs between shards and/or the config server that may result in the impossibility to balance the sessions collection.
This state could be reached - for example - due to users manually manipulating the sessions collection via direct connections.

Purpose of this ticket is to provide a remediation (ideally self-healing) to apply on affected clusters.