AD, client PC, documents folder redirected to a file server and there to a share’s subfolder (e. g. //fileserver/usershares/%username%), CSC enabled by default (standard as of Windows Server 2K8 FWIK), multiple domain users logging in to that client. While logged in as User1, the Sync Center reports errors as Error while syncing //fileserver/usershares/User2: Permission denied.

For those who, like me and after browsing 9000 of these pervasive helpless "expert forums" ("just run as admin, that solved everything for me!11!!1") and short before switching to a better virtualization engine, here for the records and for your time-saving my findings, with a lot of thanks to one of these rare helpful blog posts. And it is just as sick and loco as you may want to imagine when dealing with Oracle.