It’s a consequence of this: Queen Mab, The Goddess
In the second bullet, @sirrian mentions that traits are stacking on multiple skull matches - this was for the old Maw trait but the same applies on Courage - and probably why Barrier fails too. This has not yet been fixed, as it turns out to be far harder to do in the game’s infrastructure than they thought.
@extraturn is right, though strictly speaking the bug is in the game mechanics not in Bone Dragon itself.
And yes, I partly agree with @ExtraTurn in the OP - perhaps a compromise would be good - I’d put up with a month or two of one troop a week in exchange for a concerted patch on fixes and QoL…