Multiple command modules disables staging

[das forscher]

This is driving me nuts and I can't figure it out.

Any time I have two command modules in the same ship, regardless of how they're attached (docking ports, KW fairings or directly attached) or whether they're manned, manned and empty, or unmanned, I lose my staging interface and my staging button does nothing.

If I toggle physics warp on and off again, I can active my engine manually and control the throttle (although that lags quite a bit), but I still have no staging interface and my staging button does nothing.

I tried wiping my gamedata folder, thinking it might be a mod conflict, but that hasn't helped.

I swear I've built ships with attached landers and stuff in the past without having this problem.

Am I just crazy? Has this always been how KSP functions or is something totally messed up with my install?

[TheFlyingPigs]

1. Do you have any other mods?

2. When you load, are there Kerbals inside?