More like a geodata files issue, itself, I would say. I tested the same scenario and mobs stuck on wall or simply go through it, don't disappear / fail into texture / a (geodata) hole. So, before saying it's pack issue, better check your geodata. Since there isn't perfect, bugless geodata.
The only issue from pack is, mobs movement (pathnode) is not reworked, yet. Obviously, the pack isn't perfect and has (many) issues.