@fenderman thanks for the update. Couple of quick questions if I may:
1) Are you using the same SD cards as mentioned above ?
2) Anything show in your logs RE: Hot Swap or Disk Error at all ?
3) Are you running a customized bitrate (I know this one's a stretch but trying to isolate what makes the camera lose these quicker and this was an area I wanted to dive deeper on based on something I noticed while testing).
4) When you saw the issue before (prior to the 2019 FW) did it manifest itself the same way (logs showing Hot Swap and card disappearing) ?
If everything else is equal and the issue is still present then
maybe it is down to a particular batch and is hardware related or depending on settings etc is some anomaly in FW. As mentioned above I personally found the 2019 FW had the issue quicker than the older FW which is quite the opposite of your experience as you mentioned.
Hoping that together with
@EMPIRETECANDY and Dahua we can get some quick resolution to this because I'm running out of ideas to try and variables to test
Thanks again