Magnetic/program compass and azimuth on the map are different. Why?

[8850]

Where does the error lie?  What am I doing wrong? Why are LocusMap maps showing the wrong azimuth?
   
I am standing on a hill, LocusMap shows to the second hill azimuth in a straight line of 250 degrees.  The compass in LocusMap shows a different azimuth - to the second hill as much as approx. 263-282 degrees. Smartphone is level vertically and horizontally. The compass built into the smartphone's firmware shows the same value as the compass in LocusMap. I aim through the magnetic physical compass in my hand and it shows the same value as the smartphone's compass. Why are LocusMap maps showing the wrong azimuth? The difference varies from 10 to 25 degrees of azimuth despite accurate aiming.

LocusMap Silver 4.21 (offline openstreet map - www.openandromaps.org)
GPS excellent signal (Glonass, Baidu, Gps).
Xiaomi Note 10 PRO smartphone
Physical compass on the hand made in Ukraine
OruxMap app also shows a different azimuth on the map to the destination than the built-in compass

[Menion]

Hi,
it should be most probably affected by the "True bearing" settings. Check the app's Settings > GPS & sensors > Use true bearing and disable this option in case, you want to get identical results to your physical compass.

[8850]

Unfortunately, this option does not work. I have tried enabling/disabling all features:
GPS and sensors > Use true bearing
GPS and sensors > Comatibility mode
As well as calibrating the compass every time. There is still a large discrepancy in degrees between the map and the azimuth to the second point. These difference values are a minimum of about 7 degrees, a maximum of about 30 degrees of error and inconsistency.
How to solve this problem?

[8850]

@Menion Do you see a solution to the problem here? Do you have any ideas?

[Menion]

I'm searching through that app code, but I'm unable to find any reason for this behavior.

In case, you disable "True bearing" in the settings, values should match values from your own physical compass. It is a good place to start. You wrote, that in this case, values in the compass screen are identical to the physical compass, right?

Fine. On the map, the values are computed from the coordinates. The result of this is "True azimuth" so the final value is computed as "Computed bearing - declination". You know the coordinates of your location and the target and the declination reported for your location is visible on the compass screen at the bottom, so you may easily verify that the visible value is correct.