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?