It's been broken for long long time. I wonder if you officially stop
supporting it or it is in the plan to fix it?
The core of the problem in inability keep read-only status and VC lock
status in synch and file correctly
Try to start modifying r/o file. It will offer to lock it using VC or file
system. Using VC does not work (you will just stay on dialog clicking ok
button forewer). You can clear status using file system option but then you
are for a nasty surprise - it will switch file r/o on its own and will
insist on it even if you clear r/o flag externally to idea.
If you managed to do any changes while status is r/w you will not be able to
save them you will get access denied on save. What you will see is r/o loc
icon and modified icon on file tab. At this point savin anything or even
switching to other app will bring access denied popup every time. clearing
r/o attribute externally does not help - idea stubbornly changes it back.
One work around is to enable lock on checkout but that does not work very
well either - you will get file changed on disk and in memory and to
continue with unlocking you will have to accept file version which will vipe
out all your changes in the file