Server Version#: 1.19.3.2843 (Mac OS)
Player Version#: various
I recently moved my server to a different machine. Upon than I had to change the path to my local music video.

The change is properly recorded in ~/Library/Application Support/Plex Media Server/Plug-in Support/com.plexapp.agents.localmedia.xml
<?xml version='1.0' encoding='utf-8'?><music_video_path>/Users/eckart/Music/MusicVideos/</music_video_path>
However, the server still looks under the old path. From the log:
May 31, 2020 15:35:36.117 [0x70000324b000] ERROR - Error opening file ‘“/home/music/MusicVideos/The Rolling Stones - No Security Tour-concert.mp4”’ - No such file or directory (2)
Yes, I waited several night for the server to pick up the change.
Only, if I add a music video to an artist that did not have any before, that one will be registered under the correct path.