Here below the answer of Carenado support for the same issue :
"X-Plane now automatically randomizes the gyro drift when starting from cold and dark. Here are two ways to work around it for now:
A) Assign a keyboard key or joystick button to Nav & Radios --> Indicators --> "vacuum DG sync to magnetic north". Simply press that key or button after the plane has loaded, and that should sync the gyro drift.
B) Alternately, you can edit the aircraft's .acf file to permanently fix this (we'll release this fix in an upcoming version) :
0. Make a backup of the plane.
1. Open the "*.acf" file in a simple text editor like "Notepad++" for Windows, or "Text Wrangler" or "BBEdit" for Mac.
2. Search for "P acf/_otto_ah_source_type". You should find two lines, like this:
P acf/_otto_ah_source_type 12
P acf/_otto_dg_source_type 12
3. Change the "12" at the end of both lines to "11", like this:
P acf/_otto_ah_source_type 11
P acf/_otto_dg_source_type 11
4. Save the file.
Now when you load the plane in XP11.10, the autopilot should follow the HSI, no matter what the vacuum drift dataref says. This same fix should also work on other planes that end up having this issue."
PS in my opinion, for exploiting the best of X-Plane which give the most realistic flying experience, it is preferible to assign a joystick button, or a keybord key. I dit it and it adds realism at each turning point to check alignment with mag.