What model phones? Also what is the phone service. I am using a 15 Pro with Verizon. I can't imagine it is the radio that needs an update. Starting to wonder if it is the phones or the service that could be an issue.

Same here. 2017 Civic and CarPlay worked great for years. Multiple music and Maps all work perfectly. My phone only disconnects while on a phone call. It started on IOS 17 but not that often. Since day one of upgrading to IOS 18 it has been a constant problem. Honda says my car is updated and it is an Apple problem. Apple support tells me it is not them. They said they never get calls about CarPlay problems. Apple is getting real sloppy with their IOS updates. I had several bugs on my iPad and mac that I have reported. They are obvious bugs that can easily be recreated on their end. I gave the support team all the details on how to recreate them but I am waiting months for them to get fixed.