Same. My Readdle Calendar widget doesn't load properly when I boot the phone, but deleting and re-adding it works.It works pretty good for me.
There are some problems nonetheless. The most problems I have is with widgets.
Logitech Harmony old-style (pre iOS 14) widget not working. Unless that's an iOS 16 bug, then that's never going to work again, as Logitech have pretty much abandoned their software.
And, of course, the stock calendar widget removes events from view, even if they're still current, once it's 15 minutes past its start-time. This bug has annoyed me since the 2nd or 3rd iOS 14 beta! Doesn't seem to bother anyone else though.