Stuttering, but not when FInder is frontmost

OSX9.6, 8GB RAM, MBP 2010, 256GB SSD 6.5 GB free space

Kodi 17

Been running smoothly for years through all iterations. Now for some odd reason Kodi stutters through all video – except when Finder is the foremost application (w no windows open) and Kodi can be seen. Then there is NO stuttering.

That is incomprehensible. Only open apps are Kodi, TextEdit and Finder.

NB: When changing frontmost app from Kodi to Finder, video takes about 30 seconds to catch up to audio.