PCM 4 Bluetooth connection issue

[mbutchers]

I’m having issues connecting my Android Samsung phone to my new (to me) 991.2 running PCM 4.
The phone connects fine, and runs through all of the pairing sequences, but as soon as it’s paired the phone loses all of its connectivity/signal. The phone shows ‘no signal -no service’, but as soon as I turn the ignition off, it regains its signal. A similar problem occurs when trying to connect for BT music. I’m sure that it has something to do with a remote sim setting or something, but various searches (including on here) haven’t returned any logical fix. Chat GPT makes it sound easy, but of course is rarely correct.
Help very gratefully received - apologies if this has been covered before.

[FriedMarsBar]

Have you tried a PCM reset?
From memory, you press and hold the on/off button down for 15 secs. The screen will go black and will reboot and you'll see the Porsche logo.
This worked for me when I had a couple of glitches.