Trying to export a variable font I have a problem with one glyph. The problem being that the Masters are compatible; same number of nodes, handles, correct path direction etc:
I assume the error stems from incompatibility when removing overlap at the joint of the t with the c – check the node structure of the top of the c where it’s right next to the arm that goes into the c. For testing, you can remove overlap in all masters, which will make it incompatible. Then check where that incompatibility stems from.
Overlaps are usually not removed, but outside self overlaps are.
So there two shapes are not compatible:
Sorry, of course. I didn’t sleep much and was just reminded of a similar case (but with one single outline, so it counted as an outside overlap).
Maybe you can check whether the open corner of your t is going outside the outline in some masters, that would make it incompatible with the frontmost master.
I have sorted it thanks.