Whenever I download a mod, only certain components come through, sometimes only one. I might be using 64-bit but when I change the option on the launcher to run 32-bit there seems to be no difference. So far though, this has only really affected part-packs that come with a mod (except for kerbal galaxy 2 which broke my game completely), other types of mod look and work ok. For instance, when I got cryogenic engines, the engines didn't show up but the interstellar fuel switch did work.
If anyone has any ideas on how to fix this I would be really grateful.