Something causes the upper part of zombie cave to "dematerialize".
See the image. The empty parts are where I fired the jetpack.

I only got this bug when I fired a nuclear bomb (TTR) inside the cave. Otherwise it always plays ok and ive never had this bug while playing without mods. As for the incident when I had it, it first became like findude described and after some time the entire foreground layer disappeared like the upper part was digged clean.

I got it when I placed a bunker module around the object that usually carries the control chip. I were confused. At first I thought it was 'dynamic lighting'.

While playing the map in skirmish mode, I once saw Ronin faction dudes digging their way through the ceiling. Dunno if that helps at all. Otherwise, I've played it dozens of times with no problem at all.

BTW, I absolutely love this scene! The art is top notch, and the simple triggers are used for good effect. Did the Ronin hack the clone tubes to make zombies? For what purpose?

One more thing: has anyone else beat the Zombie Cave with just the pedestrian brain guy? It was a bit challenging.

I have a hunch that this is caused by large amounts of objects. Like MOSR or generally alot of particles.
I think this because my TTR nuke spawns lots of ADoors on one instance and a whole load more of other particles that cause the art terrain to go poof. In fact, I bet the lower dissappeared aswell, but it wasnt so obvious because there was actual terrain instead of just the giant cave piece.

Second time when I caused it was Findude's C4 sprayer that spews tons of MOSR that remain active until they are destroyed by wounds that make them explode.

I'll tell about it to data, it might a bug he accidently did. Or maybe its an engine glitch.

yes

I encountered somthin similiar I guess, I was playing Skirmish and i heard DS's coming down but i never saw any, 5 minutes in huge swarms of ROnin and coalation guys poured from the ceiling into my bnker, the cave pieves where still intact though.