Backflush movement disappear!!!

Hello gurus,

question for you!

i have set backflush for component in work order, let say we have 2 raw material, MATA, MATB, with coefficient 1:1 with the finished product.

My customer show me some confirmations (only some, not all the confirmations, for the same WO) where, in front of a confirmation of 100 pc, if i check the goods movement tab, i see 100 PC for MATA, 76 PC for MATB. that means 24 PC are missing for the second material!!!! This happens also if the GM is still in cogi. This happens for a lot of material code.

I know that, if the GM is deleted in cogi, this disappear also from the GM in the confirmation details. But my customer says that they haven't deleted the GM from COGI.

Do you know if there could be any other reason why the GM is deleted form the confirmation, except this one????

Thanks in advance.

M.