I’ve been getting that but seems like when I have a good connection and then I make a quick stop and I turn the car off. Drop kids off and back in the car in a few minutes. Then when I turn car on the iPhone has trouble reconnecting. Happens like once a week ish.
Quicker solution is shut the wifi off on your iPhone. It will say car play will disconnect and you say okay and then grom will reconnect CarPlay automatically and usually problem fixed. No need to turn off car.
I have experienced this as well. I tried turning off bluetooth and on again but it wont go away unless I restart.
The service rep asked me to take a log dump when this happens by pressing next track button and previous track button in succession and grom will dump a log file. Never cared to send them this file.
I never tried toggling wifi as I though wifi should not be having any affect on connectivity with grom as it uses bluetooth. Will try it next time and update if it worked for me.