It's pretty self-explanatory.
Longer version: whenever I try to add the TVR adapters to my craft in either the SPH or VAB, they disappear - but the price still increases as if the adapter was there. To make matters worse, I also can't launch anything until the disappearing part is truly removed - and apparently the only way to do that is Ctrl-Z. How do I fix this?
Another part that vanishes during the assembly and causes problems is the FL-T400 fuel tank. I'm sure that there are other parts that are affected by this as well.