So when I hear the word "linseed" the first thing that comes to my mind is OIL. Linseed oil is from flax and it states in the ingredients- Organic Flaxseed (4%) , this might be how they are cooking the corn thins...
Did you also notice right above ingredients it has the breakdown of fat/chol/sodium/carbs/fiber? On a 2000 calorie diet, it states "less than 65g total fat"! That could mean 64g of fat per serving (2 slices) and it wouldn't be lying to you. The sodium levels also look crazy high. Jeff N would definitely have a better answer for you but this looks suspicious to me.
Corn Thins have different varieties. We buy the Sesame ones with the ingredients 97% organic corn, 2% organic sesame seeds and sea salt. So the one with flaxseed is one of the varieties.
If linseed oil were an ingredient they would have to list it. So the ingredient is flaxseed, not the oil. Having said that, they can claim 0 fat if the fat ingredient is less than .5g per serving, but there would still have to be oil listed in the ingredients, which there isn't.
The Percent Daily Values breakdown is listed on all labels as a reference for what they are basing the percent daily value on that is listed in the nutritional breakdown. So the less than 65g fat is a reference to use for calculation, not the fat that is in the product.
It's possible that this variety doesn't agree with energy_dad because of the flaxseed, or perhaps it was a one time occurrence, or there's just something about the product. Like I said, we buy the Sesame variety which my DH eats all the time with no trouble. I love them but stay away because I'll eat too many and they are higher calorie density.