HEMTTs werent problems. No more or less than any other wheeled vehicle.
I will try to explain the pacer item. In an Armor Battalion (and Im making up the #'s here for easy math), say there are 100 M1 Abrams Tanks (which is VERY far from the truth). Army regulations allow for only 5% of the tank fleet in the battalion to be broken (not FMC) at any time. So when that 6th tank breaks, it's a big deal, and one of the 6 broken tanks needs to get fixed TODAY, so we can get back to only 5% being broken. When you have 100 tanks, you can have up to 5 broken and things are ok. When you have 1 M985 in the battalion, and it breaks, thats 100% of that "vehicle fleet" is broken... Thats BAD. But the flip side is when that 985 is running, 100% of that vehicle fleet is 100%.
so when the M985 broke, it was a big deal to get it fixed.
I had a ton of M977's and M978's and they were great. I also had the 1st 3 XM1120's LHS in the Army. One of them being armored, and no AC.