I'm having the same problem, but I don't have the calendar snooze app.  Was happening on Pixel 2XL.  Verizon suggested I needed to replace the phone, which I did.  I now have a brand new Pixel 3XL that set me back $600 that has the exact same problem.  Verizon, have you figured this out yet?  Any one else have suggestions on other apps that may be conflicting?  I also turned off battery optimization for anything remotely related to the the phone app or services.