This is a defect, though it may be noted in the content release notes.
before the fileserver was restricted in the exports-file as follows
this isn't sufficient now. Must I just set the "user=bladmin" or to which commands can I restrict the execution?
For the install it may need more - so drop the commands= for now.
or you could look in the rscd.log on the file server and see what command it's failing on and allow that.