1. Start 'emacs -Q'
2. Record simple macro "C-x ( C-p C-n C-x )"
3. Bind macro to a key (tested with <f12>, but reproducible with others)
  "C-x C-k b <f12>"
4. Edit bound macro "C-x C-k e <f12>"

Edition fails with following msg:
oclosure--get: Assertion failed: (eq 'closure (car-safe oclosure))

Stefan, any ideas?

Should be fixed now on `master`.