(Pack version: 1.0.4, no other additions)
I was able to clear one slice map using a campfire, but subsequent attempts to clear maps only results in the campfire being marked. Neither right clicking nor shift+right clicking work. Breaking and replacing the campfire also didn't solve it, nor did breaking and replacing the hay bale underneath (both with another hay bale or with another block). Additionally, clearing the slice map resulted in it being turned into a regular map.
Sorry if these should be two separate issues but I don't know if one caused the other or if they're related at all.
I've attached a video showing the issue (the second map was previously a slice map for reference) -