If coupon scans, but are used for wrong size or slightly different product:
(i.e. using Huggies surpreme diaper Q for Huggies sung-n-dry diapers.
or using Special K with berry cereal coupon for Special K with chocolate cereal
or using 12.4 oz- 41.6 oz PHillsbury frozen buiscuits and dinner rolls coupon for 10.00 oz phillsbury frozen buscuits)

even if the coupon scans and goes through,

it is a coupon fraud, right?

Mistakes do happen, but I would be careful to make sure your coupon matches up with your item. I'm not sure if the store still gets reimbursed for the amount if the item is different, they could get cheated out of the coupon amount and make it harder for couponers to shop by really scrutinzing each q. Sorry for the run on sentence!