After I conducted extensive tests, I discovered it didn't depend on any extreme values.
Download this:
https://www.dropbox.com/s/krghpqppn2gub ... m.zip?dl=0and use it as aircraft (called "SubmodelAim").
First you can try varying the values in property tree under aim/ and see how it aims flawlessly with any values.
But once you start changing the "aircraft" orientation too, things get tricky.
Set these values:
orientation/ heading-deg=80 pitch-deg=15, roll-deg=25
aim/ pitch=85, yaw=110
And the submodels will aim way off from the red aiming aid. Now you can see that slightly varying the values can have huge effect on the offset.
And note that all the values are in the expected ranges, whether it is 0,360 or -180,180 for yaw.
The reason why I had to use huge pitch and yaw values was that my aircraft pitch and roll were very small, less than 0.1deg.
Tom