It's definitely related to internet connectivity.  I have tried changing the settings in the firewall to block inbound and outbound access to QB, however, the program still seems to find a way to connect because even if I block all access in and outbound and open QB I can see it is connecting to the internet (for example, the box in the lower right corner load with COVID help and the discovery hub will connect to Intuit - these will NOT work when I am offline).  Regardless of the firewall settings I still have instability in the app with crashes.  The ONLY way I have found to repeatedly eliminate the crashing is to open QB only after taking my PC offline (by shutting off wifi).  This has worked all day.  Nothing else has.  I have been able to turn the wifi back on once QB is running and it seems to be OK but have not tested that extensively.  Since there's no reason to have connectivity I just leave it shut off while working in QB, then, once I quit out of QB turn my wifi back on.  It's really not a big deal and seems to solve the problem.