This is a ANGLE. You can't use vector expression. Try this again;

vec_set(trail.pan,my.pan) and delete "trail.pan=my.pan" expression...

Or,

vec_set(trail.tilt,my.tilt) and delete "trail.tilt=my.tilt" expression...

Or,

vec_set(trail.roll,my.roll) and delete "trail.roll=my.roll" expression...


If you want to play x plane, define a vector.