My GM-made car does indeed have connectivity issues with CarPlay at least a few times a month. Turning my phone's Bluetooth off and on again fixes it, which makes me wonder if the problem really is on the phone side.
On the other hand, it happens more often when switching between a built-in car app (like the 360 cameras app) and the Carplay app, which probably implicates the car's software more?
In any case, it is pretty annoying. It sometimes happens at really inopportune times, which can be a distracting safety hazard just from the loss of connectivity/functionality alone (i.e. not even considering needing to touch the phone, which is illegal while driving in many US states.)