Necroing because I had the same problem.
I used te5edit to check that changed the item weight;
It is a popular mod, Immersive Jewelry SSE
"This crafting system is an expansion of the standard ingot smithing system and does not alter it, other than material weight. "
"Q: I hate having realistic weights for the vanilla ingots! It's perfectly fine with me that they go back to weighing 1 feather each, even though the new 1/10th portion bars included in IJ weigh more than 1 feather! For that matter, I hate having weighted septims too!
A: Really, try the "Exchange Currency" mod by UniSL. It was designed with Immersive Jewelry in mind. It adds a dialogue option where any shopkeeper can turn your heavy septims into really beautiful and immersive lore friendly banknotes. As for the heavy ingots, I think it's a bit silly not to want them, and the fact that they were left at "1" when dragonbones weigh 15 is probably a dev error..."