Version 1.21.1 has been released. This version fixes crash while building VIS data and crash in Hexen when traveling between maps.

Hexen crashes when building the vis data (the same happened with 1.19 version)

Dev: Loaded MAP01, 2236 vertexes, 5145 segs, 1039 subsectors, 4290 portals - VWadFile::BuildPVS - W_BuildPVS - VLevel::LoadMap - SV_LoadLevel - SV_SpawnServer - COMMAND Map - VCommand::ExecuteString - VCmdBuf::Exec - Host_Frame ERROR: Leaf portals saw into leaf

This is a different problem caused by latest glBSP. See bug reports forum.