Seeing as this is obviously a webwalker problem, i'll use the old walking api for the parts covering the bank and the upper ladder. I can't guarantee this will fix it, but im very confident it will.
EDIT: I've pushed a fix and hopefully this should now be resolved. Tried it a few times and the walking seems good. The script shouldn't load webwalking until it reaches the ladder at this point while using local walking on the parts that isn't inside the edgeville dungeon. As always, there will be a few hours before the update is live.