This is odd.
Last night I cut a friends (okay ex-gf) wedding video she was involved in.
For the heck of it I went Optimized ProRes 444 at 4K UHD.
After about an hour and maybe a 4.5 min timeline, I started experiencing the gripes folks have expressed here.
Now this is the first time Ive used ProRes 4444 and usually stay at at R3D RAW.
For the fun of it, Ill take the same project and delete the optimized files and redo with HD res and see if I can choke it.
Files reside on a SAS R680 GTECH eS Pro 12TB system running of a 2012 Mac Pro with 32GB and 512SSD as host drive.
Again never had this issue with super long format edits.