There is an intermittent issue regarding crafting that I have never been able to confirm.

In theory, and the way it's supposed to work, is that we get 1 weapon upgrade level per character level, right?
If the character is level 16, we can upgrade the weapon a max of 15 times as I understand it (depending the weapon level when we find it).

I have been at a lower character level when mass-upgrading a weapon, and sometimes that weapon disappears from the upgrade screen and NEVER SHOWS UP AGAIN.

However, I have tried spawning the same weapon through the CET console, and given myself enough resources to upgrade the weapon from level 1 to level 50 in one sitting...and the stats displayed in the inventory are identical to the one that "disappeared".

The only exeption I have experienced is if the weapon in question is a Unique, and I upgrade the rarity. THEN it shows up again in the upgrade screen, and can be upgraded further as normal.

So my theory is that it is not so much a bug as a glitch, where the game suddenly upgrades a weapon for free for the rest of the playthrough, making it scale without cost like the old Skippy used to do.

Only way to prove this is by taking a screenshot of a weapon in the inventory that is not visible in the upgrade screen, and keep taking screenshots with every character level increase to check the weapon stats (something I keep forgetting to do every time this has happened to me). To verify whether the stats stay the same or increases for free.

Though I have no idea what triggers this "feature" to occur.