I haven’t merged all the parts making up each letter; there’s a lot of overlap. Other than that it’s fully compatible across masters, so I’m guessing that could be the main issue. Is it customary (or necessary) to remove ALL overlaps when making a variable font? Or maybe it’s just an issue with Cavalry?
It is a bit tricky to see. But it seems that the path direction is wrong. All black paths need to be counter clock wise. Wrong path direction can cause rendering issues.
And do you need the gaps for anything (e.g. is there a “gap” axis?). Add a tiny overlap to avoid gaps.