In my situation, a matrix Formula was evaluated at random values for the variables, leading to a comparison of something with all zero entries with something else that *should* have had zero entries, but the decimal arithmetic and numerical matrix multiplication was making something with entries that were slightly off. Off by enough to get a comparison like "0 == 0.000000001" which returned false.

### Re: Matrix custom answer checker not returning Value->Error messages

by Alex Jordan -In my situation, a matrix Formula was evaluated at random values for the variables, leading to a comparison of something with all zero entries with something else that *should* have had zero entries, but the decimal arithmetic and numerical matrix multiplication was making something with entries that were slightly off. Off by enough to get a comparison like "0 == 0.000000001" which returned false.