When playing Realms of Zoon (here: https://forum.zdoom.org/viewtopic.php?f=42&t=54781) some textures fail to appear, or fail to appear correctly. The author of the mapset suspects there maybe a problem with 3DGE reading 512-high textures. Here are some screenshots of the issue: https://www.sendspace.com/file/dxce47
This has been fixed in the devbuilds =)
Marked as fixed.