Backflush

Dear Experts, Good Morning!

I have got an issue like this...

We have got a Material 'A' with BOM Level 3 in BOM,which is used in a Vehicle Model JS200. This same material is used in JS210 too.

But in the first model Backflush is not working for Material'A' and for this same material Backflush is working in JS210.

What would be the reason for this??

Can any one help me???Please...

Regards

MK