Looks like a lot of folks are having this error.
For me, it's when I try to play a 4k UHD rip. I have a 4k monitor - though something about HDR settings (identified through DVDFab Media player used to confirm the rip is good) might make it want to transcode?
Either way, when I click on the movie I get the shaka 1001 playback error. Only on the 4k movies.