I've got the same bug.
At a given time (not sure when), skeletons of the kind summoned by "If their Bones Still Slept Under that Hill, None Can Say" started to appear in random positions in all maps, even unexplored ones. Also, summoned skeletons started to persist after combat.
This has proven to be a most entertaining bug, but it kills atmosphere to enter a supposedly barren land to find it overcrowded by skeletons, or enter a villager's home and find skeletons on its ceiling.
Please find the diagnostic files for a game after the bug triggered here:
https://www.dropbox.com/s/ia8h0232ksft9vp/PoE_skele_bug.zip?dl=0