Why does my phone hang up sometimes

I got a response from Shift today. The solution seems to be working at least so far. There are also tips on Bluetooth problems. But I haven't tried it yet.

Maybe it will help you too

The fact that the phone calls are interrupted could be due to the double-tap function to wake up. Please deactivate this function once under Settings -> Display -> Advanced -> Tap to activate
Otherwise it could also be due to the proximity sensor. Please install the Sensors Multitool app once (from Wered Software). In the app, use the three bars in the top left to select the menu item "Proximity". Now move your cell phone at the level of the camera and loudspeaker from further away towards the cell phone. In the app, the indication should now change from 1cm to 0cm when you come very close to the display (almost touching it). If this is not the case, the proximity sensor is probably defective.
You can also use the app to test how you have to hold the phone in order for the proximity sensor to react. This ensures that the display is locked when making a call so that the face cannot operate the display. If you hold the cell phone a bit crooked, the proximity sensor may not be able to detect your face.
With regard to Bluetooth, try to delete the data in the Bluetooth app. This usually already brings an improvement. Under Settings -> Apps & Notifications -> App Info -> 3 points -> Show system processes -> Bluetooth -> Storage -> Clear cache (if that doesn't help, then select Clear data once, after which the devices would have to be paired again )
Also deactivate the function "intelligent energy saving in standby mode" under Settings -> Battery as a test

Click to enlarge ...