CarPlay stays in sync with your iPhone. If you pick up your iPhone and switch out of Google Maps (or Apple Maps, for that matter) to another app, then your CarPlay screen will switch too, by design.
Is everyone running the latest version of iOS? (13.3.1) Are some iPhones more prone to causing this than others? I have an iPhone XS -- I do sometimes experience some issue, but it's always fixed by unplugging and replugging in the iPhone, and reboots have become very rare.I'm having isssuesssss with the new google maps. I like the sat view on my maps and I think its interfering with the rest of the headunit's system... yesterday when I got out of work...plugged my phone in. Took a call and the entire head unit froze up and rebooted twice...so frustrating. I see some other people experiencing the same thing over on the accord forum. Some have had their car in the shop for weeks with head unit replacements and still no fix, its definitely software not hardware...