BSP Anomolies... WTF?!

[mister2]

so im just about done with my first map... yet every build has at
least one phantom wall, or floor, with collision only for projectiles.
i cant see the surface, but i can stick a plasma to it, and it blows up.
rockets hit it, and they too blow up. bullets hit it and they dont continue
to their destination. its just as if there was a face there, but textured with
100% transparency. but i didn't put any face there, as it makes no sense.

first time it happened, it was a narrow rectangle in a small trench,
spanning the gap from the regular floor level and across the trench.
then i had to make changes elsewhere in the map, and in the next
build, i got a new phantom collision surface sticking off a catwalk...
anyone have a clue where these could be coming from? i KNOW for
a FACT i didn't build these into the model, so it's beginning to seem
like a glitch somewhere in the compilation... maybe tool?

[killzone2k3]

make sure u didn't create any faces backwards in 3ds or gmax because then ur texture is turned the other way but the solid face is still there making it seem invisible.

[mister2]

thanks, but i didn't do that. that was the 2nd thing i learned about modelling. not to mention i never would have put a face there. and if i did, STL check woulda picked it up, and if it didnt, tool would have complained before ever compiling the collision model. ive analyzed the areas in 3ds max, theres nothing. in sapien however, i can place scenery in the air, where the invisible face is. so its got some kind of collision, but in game, only nades, bullets, and effect particles can touch it, master chief cannot stand on it. also, i KNOW it's not something that i created, that's being left behind or something, cuz the one i had the first time, is now gone, after i made zero changes to the area, and theres a new one near a different platform. so its very glitch-like... i really dont know if i'll find a solution unless someone else has experienced this, cuz its not a face that i created. grrrrrrr