Knocked Out Thralls still fall underground (alot). After knocking out a Thrall, many times it will fall into the ground, You have to run out of rendering distance and return to get it to pop back up. Usually happens in the mtn. areas and lowlands around the west side of tower.
AMD Rizen 3 2200G w/Radeon Vega Graphics 3.50ghz
64bit Operating System and processor
Windows 10 Home