See LPP-31308 for details and reproduction steps.
Summary of issue:
When a DLFileEntry is deleted on the server, its associated Resources are deleted here. This triggers Sync Connector's ResourcePermissionModelListener.onBeforeRemove(...) which updates the modifiedTime here.
After the DLFileEntry is deleted, the code will hit SyncDLObjectLocalServiceImpl.addSyncDLObject(...) as expected w/ a "delete" event, but now the database's modifiedTime is greater so the method exits due to the future time check here.