Plex Media Server beta 1.13.7.5369 has just been released. It has a fix for the problem that arises after changing from a multi-location recording library to one with one location path only
See Release Note Plex Media Server
- (DVR) Changing destination library from one with mulitple paths to one with a single path for a DVR recording no longer causes a recording failure (#7551)
[Please note there is a similar bug in Plex for iOS that arises when changing the recording within the Plex for iOS app - this has been fixed and the fix will be released soon]