This is one of the more hairy topics to approach. However, I have a failsafe way to handle it. Basically, each chunk can contain 4 textures (each on a layer), which each can have a specific applied groundeffect ID. The ID is further defined within the .dbc, however, this is not important. The most important thing is simple; Wow tries to visual a groundeffect for a texture that is not existing. On a chunk with 3 layers, but 4 ground effects noted, it is bound to lead to a "false", leading to a crash.A simple fix is easy; simply use the texture painter, apply some texture, set it to some size but the lowest speed and apply it onto the adt, until every chunk has 4 layers. The crashes stop.Another possibility is to remove all the groundeffects IDs (MCLY) for every chunk, or even specific chunks, to avoid the problem. Refer to the 010 Editor for that.The last one is to completely change the groundeffects according to needs. Either by hex, or getting a tool (post it once you have it.)