Image previews missing in Capture One 20

Since early September, image previews have stopped working for me in CaptureOne 20. I use session workflow and this happens with all sessions, no matter what the size is.

I use a 2018 Mac Mini, with 32GB RAM and a maxed out i7 processor (based on suggestions from this forum).  I briefly tried it with a Apple approved eGPU and I have the same problem.

I filed a ticket with CaptureOne.  We went back and forth on many solutions.

* My images were downloaded to a 2TB SSD drive connected to USB-C and the session was on the primary 500GB SSD. I was asked to not use the external SSD.  The problem happens in local disk as well.

* Uninstalled, deleted all preferences, reinstalled, same issue.

* I have tried to select all images, force regenerate previews, it works for a bit, but if I quit C1 and restart, previews go away.  For larger sessions, browsing up and down loses preview.

After nearly a month, C1 accepted it was a bug and filed one, but they won't fix it.  This is the last response I got from them.

Capture One is unusable for me for ingestion and browsing. I was anyway looking for a catalog management software, so I ended up spending $229 to get Photo Mechanic Plus and I know use CaptureOne as only a RAW editor - I have one session in which I open the images and edit.  This is the same folder in photo mechanic.

Anybody else seeing this?  Any suggestions on what to try to fix it?  I am wary of updating to 21.   I already regret buying 20 (it was un-needed upgrade) and I don't want to spend any more money on Capture one when they won't fix to what to me is a blocking bug.