Why are don't my headphones turn on and instead factory reset?

I had the same problem and finally managed to fix it, The headphone jack still worked fine with the headphones too, so I’ll share in case it helps someone else.

After doing a full factory reset (following the manual exactly), I could reconnect the device over Bluetooth. However, every time it powered off, the issue came back and I had to repeat the factory reset to use it again.

What actually fixed it for good was this:

1. Perform a full factory reset so you can connect over Bluetooth.
2. Once connected, open the Sony Connect app.
3. Use the app to update the device’s software/firmware.

After updating the software via the Sony Connect app, the problem stopped happening and I no longer needed to factory reset it each time.