There is an issue with the Forge where it doesn’t show an issue when you try to forge something that has 3 Prefixes or 3 Suffixes. With 1.2 (as with earlier patches as well) some Affixes moved from being a Suffix to a Prefix, and I would assume possibly the other way as well.
This leads to an issue with the Forge. I had an item that had only 1 Prefix. I didn’t notice the breakdown as it was in my stash, but I noticed it had FP so I popped it in my Forge and when I saw it had an open Prefix slot I tried to add one. It wouldn’t do anything.
The problem was that the Forged didn’t identify the issue of why I couldn’t add another Prefix. The item and prefix matched but I couldn’t figure out why it wouldn’t add it. It wasn’t until after I removed it from my Forge and looked at it that I noticed it now had 3 Suffixes so the number of Affixes was maxed. This should be identified by the Forge in my opinion.