Corner component flipping when aligned to a vertical stem

I’m having an issue with a corner component that’s been designed as a curve with some overlap. When I attach it to a curved shape it works fine, but when I attach to a vertical shape it flips horizontally. If I shift the point below by 1 to the left, then it flips back the correct way.

Here’s how the component looks:

When attached to a vertical it flips horizontally:

When I shift the lower point by 1 to the left it’s oriented correctly:

I have these aligned left since removing the alignment squashed the lower curve too much, although removing the alignment did resolve the flipping issue.

If needed I have a small test file I can send. Using Glyphs 3.5.1 (3534). Thanks for any help!