When you hide with h button skybox and then unhide it then it might cause problems with compiling and error appears in console couldn't load portals (.prt error) appears. After 2 minutes I can then without changing anything in skybox compile map without a problem.
When you hide with h button skybox and then unhide it then it might cause problems with compiling and error appears in console couldn't load portals (.prt error) appears. After 2 minutes I can then without changing anything in skybox compile map without a problem.