A set of rule working for 1 model but not for another (two models are similar)

 Hi All Experts ,

We have two models say A and A1. These models have the same structure except for 1 option class out of 27.

For the other common classes . we simply created rules for A1 (new) with ref to A. I mean we use the same logic and rules are also same except for the diff items/options.

I have just 1 class out of common wherein this logic is not working . It works for the older moder A but not for new model A1.

Can anyone suggests why this could be?

Thanks,

Prasad.