Some official Nintendo 64 gear not compatible with itself or hardware problem?

[seastalker]

I had purchased a bunch of N64s and accessories in an auction, and cleaned them up and did repairs where needed.  When all was said and done, I had one game that didn't load on any of 20+ systems sitting in my 'rainy day advanced attention pile' along with some touchy controllers, jumper paks and expansion paks.  

 

My own N64 no longer likes my official red top expansion pak so I have a jumper pak in for now.  This weekend, I got a steal on another N64, and it had a red top so I thought to put it in my own...  TWO bad red tops?? So, I learned that both my 'faulty' one and the new one work fine in the recent N64 (both Nintendo original) but neither expansion works in MY N64.  I also found that the old crap game I thought was dead booted instantly on this weekends N64 no problem, 1st try.

 

I figure I will keep the game paired with the newly acquired N64 as they must have been married in a past life.  Anyone know how or why perfectly good official Nintendo red top expansion paks won't work on mine, or if the N64 is just finicky with some hardware combos and I should just keep trying with red tops until I find one as happy with my system as the crap game was finding a love match?