I bought the "Chaferfu" spell from one of the NPCs at [0,1] or so.
Then I ran the Skeleton dungeon. The NPC in the exit room does not have any dialog option that allows to leave the dungeon.
Selecting the spell variant "Chaferfu Lancer" looks marginally more promising with an extra option in the dialog path beginning with "Ask what the secret is", alas that extra option only leads to a loop.
Thanks!
How to reproduce is detailed above already.
What would you like to see on a screenshot? That I can't get out needs evidence of absence but all I can provide is a movie or absence of evidence.