The Wyoming scale guy told me a couple years ago that it is not legal in WY to do commerce off a split scale weight (for much the same reasons as mentioned above.)  In your case, if that were the law, it would probably bite you in the backside by forcing you to do something different unless you could argue that they must accept the full scale weight.

I would make a call to your state weights and measurement department and ask that they check out both scales.  One is not accurate and should lose it's ceritification and be shut down until it is functioning properly.  And then you are probably bit in the backside again.