Cannot configure function of AES stylus button
The AES pens which have recently been added to libwacom have one configurable button and one "eraser button". The control panel currently provides a reasonable-looking fallback UI for these pens (see #1017) but it is not perfect. One particular issue to be called out is that the configurable button does not seem to be modified by the "Button" dropdown in the UI. Changing it from "Default" to e.g. "Forward" doesn't seem to make any difference to the button's behavior.
I'm guessing that g-c-c may be trying to program the "wrong" button (or Mutter applies the setting to the "wrong" button) under the assumption that two configurable buttons are available.
Recordings of button clicks are available in #1017 for debugging and testing.