Fairphone 3 rebooting in sleep mode/jack issue?

Hello

Had my Fairphone 3 for about 6 weeks, a few teething issues were sorted out after the first update, however since plugging headphones into the jack for the first time, it’s started constantly rebooting when in sleep mode. No idea why. Phone stays on and works fine now I’ve taken security locks off, however as soon as the phone tries to sleep, it reboots. Any ideas? I’ve reported to FP but no response as yet.