Tommy,
I think there is some psychology to slumps on particular golf courses. I recall a hole on the course my HS golf team played, with a real narrow chute for the tee shot. Somehow, I got it through the first time I played, and never had trouble with that hole. Others could never hit that narrow fw.
There is also the old horses for courses saying which could mean it would be a bad time to slump break if you are playing a course that doesn't fit your game. If your game is such that no course fits it.....hmm.
Other than that, yes slumps are a mystery. I will say that of all the pros I know, they could tell you if they were going to be top 5 that week based on their practice and prep, and somewhat based on how well they felt they could play a certain course. By contrast, I am sure they know the weeks they have no chance to win.
As to long term, I recall playing a grand opening with a well known DFW area pro from the last generation. He was in the midst of a very long and well publicized slump, and even shanked about half the shots he made in our little 9 hole exhibition. At some point, it must be all between the ears, methinks.