I have found a pattern for this. It is a WIRELESS CarPlay issue only. Wired CarPlay is just fine from what I've experienced. Yes, Wireless CarPlay needs WiFi to work, but it establishes a bluetooth connection to the radio to let it know it's there. I have a 2020 Tundra with a 10.1 DMX1057XR unit in my truck which has wireless CarPlay, and my wife has a 2019 Honda Pilot with wired CarPlay only. I was able to break hers when I plugged into my truck, but was unable to break mine plugging it into her vehicle. I do not use Wireless CarPlay in my truck, but the fact it has wifi in the radio, is what causes the issue. I disabled Bluetooth on my unit, and it no longer breaks my connection. I am able to receive calls on my watch after leaving CarPlay. I'm not a huge fan of wireless anything, so using it wired works great for me. I hope this helps others.

I'd like to update again that just disabling Bluetooth does not fix the issue. Wi-Fi would need to be disabled on the radio and use wired CarPlay only. I went back and forth a few times with Wi-Fi turned off on my 12 Pro, and it didn't break the connection. I however can't disable Wi-Fi on my Kenwood DMX1057xr, so I will be looking at other units.

That didn't work for me. The real test is, the watch and your phone have to go in your vehicle and leave the current wifi wherever you're at. If the watch stays at the house, it will continue to ring.