RP2 Camera 95% inoperable after October-ish 2019 update

Build number P-MR2-RC001-RZR-190914.3123, Security patch level September 5, 2019

Apx 20% used space on 64GB SD card formatted as system memory, 30% used system memory.

Camera seemed to work mostly OK before this, except I had the issue with the camera freezing on zoom.

Now when I start the camera app, one of two things happens:

1. Screen overlay and buttons appear immediately, but no image from the camera for apx 20 to 30s. Sometimes switching front/back will speed this slightly, but it's NEVER immedate.
2. I get an error that says "Can't connect to camera", and when I hit "dismiss" the app closes.

When the camera comes up, it takes pictures OK, and does not seem to have the zoom freeze issue.

I have tried third party camera apps.

I have tried disabling camera access permission to every app except the camera.

I have tried properly ejecting the SD card and rebooting. Camera refuses to do anything - "SD Card Ejected - Insert an SD card before using the camera".

I tried a different SD card formatted as system memory. Camera continues to refuse to work without the old SD card. I suppose I would have to "forget" the old card, but I'd rather not do that yet.

More suggestions?