This is the suspected RDP issue and use of per session temp directory for terminal services sessions
Relates to this windows registry HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\PerSessionTempDir
Have you launched Plex Media Server in an RDP session?
It appears that %TEMP% cannot be relied on when the above is true
See this forum thread post and rest of forum topic https://forums.plex.tv/discussion/comment/1477456/#Comment_1477456
You can see from the above the log extract that sqlite3 used a temp directory C:\Users\ADMINI~1\AppData\Local\Temp\1\ and not C:\Users\ADMINI~1\AppData\Local\Temp\
