I'm having issues on a Newfi D2 on 19.07.2. I can see the signal drop on my PC, then the 5Ghz network goes down. When it comes back up, the router works again. This was a fresh install on 19.07 RC1 that I upgraded to .2. I tried to go into the system log, but I don't see any errors.
My current plan is to try the 2.4 network and see if I get the same problem. If that fails, I may go back to 18.06.8 - although this is a new router (to me), so who knows if that will work. I can always go back to my WNDR3800, if all else fails!