JSPitman

Hey, thanks both of you for your responses. But its turns out the issue was just me being dumb and not listening to my dad's advice from a day earlier.
He had suggested that the fuse's socket may have gotten bent/expanded, so the fuse wasn't making good contact. I brushed that asside as I was certain it was making contact, and thought I'd verified such using a voltmeter. Turns out, my tests were a fluke. He had a look at it hinself after I asked about y'alls suggestions, and he just bent the pin on the fuse a bit and jammed it in there, and now everything works perfect. (Both the compass and cruise control. Still not sure why one breaks the other, but doesn't matter now).
I guess while installing the camera fuse, I must've somehow buggered the socket up.
Eitherway, thanks again for trying to help, it means a lot to me even if in the end the solution was something else.
Moral learned, though- always trust a dad's intuition.