I’m seeing this too, in the Arrow, I’m in FS24/SU2. The aircraft does follow a heading, but always about 10 degrees off from what the HSI heading indicator is saying.
I thought to look at the still confusingly named Gyro Drift compensation in Assistence setting, but cant work out if I need that Enabled or not - to be clear, I do want the Assistence to help me. I also can’t seem to find the correct keybind, I can’t figure out what they’ve called it … (hints appreciated!)
Anyway, so yes: seeing the same.
(Edit: this is with the most recent JustFlight update at time of writing)