I've just noticed that some of my weapons in the armory (like Glacial Crystal Totem or Mobile Winter Warmth Canister) are no longer equipable to pets, and after removing them from the armory they can't be placed back. The question: Is it temporary or permanent changes? Or maybe I am facing a kind of glitch again?

As those aren't commonly used weapons, I haz no idea.

But you should totally try upgrading, there's a few cheap ones that are very good !

I've noticed some things that used to be mediocre weapons have had their stats removed and changed to just toys. It's probably the same with these items.

I had asked about an item that had stats but couldn't go into the armory anymore and was told something similar to there being a few items that won't be weapons anymore and they're slowly losing their stats. Chances are it's permanent.