Bug: course line rotating randomly while flying, IGC playback OK

I have the following bug: When I fly, the black course / bearing line is rotating randomly, sometimes it's perpendicular to my flight direction (in little to no wind). I also have a pilot asking me about this behavior on a totally different device.

When I play back the IGC, the same line is perfectly aligned.

I suspect the following is happening: During flight, bearing / course line is received from the NMEA signals, which is super buggy on most phones. In IGC playback, it is calculated by connecting the last two coordinates.

Proposed fix: Please don't use the NMEA signals for anything (speed or bearing), as they are unreliable. Instead just connect the last two coordinates, which is reliable even on cheap phones.