Motion tracking chokes and hangs

Blender 2.93.4 on Big Sur 11.5.2, 64 GB RAM. Motion tracking of 189 frames of 4k ProRes just kinda chokes at roughly 67 %, no matter if backwards or forwards (so it’s not an issue with a particular frame). It does one more frame taking like two minutes to process it, then it just hangs (can be cancelled). The previous 66 % are done in like 15 seconds.

Preloading or using image sequence doesn’t matter. Very simple drone track with constant speed, no motion blur. Any tips? Thanks.

Look at preferencies → System → Memory Cache Limit