There are threads around proximity sensor issues, as a workaround you can just turn of the screen during a call (just ensure power button is not set to end calls). Hopefully FP will fix this.
I hope that it’s just a software (calibration) issue and they can fix it. But it’s definitely not a problem of the Google dialer app. I used it on my previous phone without any problems. Only on FP4 does it behave like this.
Got it, in that case I would suggest the following (final one)