Quota can be checked in DFS management > Replication > Staging Quota

# Get folder list
WMIC.EXE /namespace:\\root\microsoftdfs path dfsrreplicatedfolderconfig get replicatedfolderguid,replicatedfoldername

# Clear quota
WMIC.EXE /namespace:\\root\microsoftdfs path dfsrreplicatedfolderinfo where "replicatedfolderguid='<RF GUID>'" call cleanupconflictdirectory

if the above does not work:

1. Stop the DFSR service.
2. Delete the contents of the ConflictAndDeleted folder manually (with explorer.exe or DEL).
3. Delete the ConflictAndDeletedManifest.xml file.
4. Start the DFSR service back up.

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references:

Manually Clearing the ConflictAndDeleted Folder in DFSR | Microsoft Community Hub