Tried several solutions to resolve event ID 4004 before finding one that worked: https://community.spiceworks.com/topic/569594-dfsr-tombstoned-folder-s. The issue can arise when you remove/delete a server from a replication group or delete the replication group itself and re-create it with the same name or same target and/or destination folders, which is what I did as a result of the datastore corruption

Apart from event logs, you can run this command in PowerShell to check DFSR status. You want to see 4s.

Get-WmiObject -Namespace “root\MicrosoftDFS” -Class DfsrReplicatedFolderInfo | Select-Object ReplicatedFolderName,ReplicationGroupName,state