Need some help: Fully custom build was fine, now having throttle range issues

[BrianG]

Dirty or poor connections would cause voltage drop, but may not be high enough to cause LVC when the pack is fresh, but as they deplete even a little, that coupled with voltage loss from bad connections could be prematurely tripping the LVC. However, any voltage loss due to connections would cause excessive heat at those points.

Seeing as you are using all MA batteries, I would suspect them as being the culprit, especially if they have been sitting for a while. I would see if maybe a friend or your LHS has some packs you can try to see if it does the same thing.

A single bad cell could make the whole pack(s) appear to be weak, but you'd think this would be readily apparent by the amount of balancing needed for a single cell.