Sidebearing gets replaced when I go to the next glyph

Steps to reproduce:

  1. Create a new font
  2. Add a glyph for A - perhaps a rectangle
  3. Add a glyph for B - perhaps a circle
  4. Set the side bearings for B to A (as reference, not value)
  5. Add a glyph for C - give it some values for sidebearings
  6. Open glyph B
  7. Select a sidebearing (say left)
  8. While the sidebearing is selected, hit Fn-Right to go to C
  9. See that the sidebearing of C is replaced with that of B (which is a ref to A)

Here’s a screen recording: Dropbox - Screen Recording 2021-08-22 at 1.52.43 - Simplify your life

I lost quite a bit of time trying to figure why my sidebearings got messed up. Is this a bug or a feature?

Thanks for finding this. I fixed it.