I didn't read all of the posts but I'd say the hardest "clocks" to work with was the old hydraulic manifold Toro's like the VT-1 thru 4 series.
I used to service these old controllers on a golf course near me and they were always clogging at the junction inside of the cabinet. To clear them you had to have REAL quick fingers as the moment the line was separated the damn head popped up.
The cams always stuck and until one became proficient in knowing how much pressure to apply the risk of striping the teeth was a constant concern.
Not to mention every station in every satellite had to be timed perfect to avoid overlapping the run times and screwing up the coverage from too many heads running at the same time.
I still cringe when I hear that ratcheting noise.
Nice Try = You Suck Spelled Differently