I solved this bugger
there are 2 reasons, but they have the same source:
the game thinks, it will spawn the player inside an entity
1.props:
most probs have a small boundary/collision box; others, like the explosion particles have a huge one, it encloses every debris of the explosion. so, specifically look for props_dynamic that use much space for their animation
solution to the explosion depris problem: set collision to non-solid
2.func-lod
lets say you make a room, select all walls, make them one func_lod
the engine thinks, its one giant object/entity, when you place an exit inside the room, the game would spawn the player inside an entity, so it destructs the exit to avoid that
in general, if you want to find out why, isolate the area, where the teleport destructs, and narrow the problem down