Not sure if it's entirely a bug, but when I researched Magnetic Weapons and upgraded to Shard Gun and then upgraded the Combat Shotgun (In that order because it's required :P) All the gun mods on my Combat Shotguns went onto Shard Guns instead of the Combat Shotgun T2

That shouldn't happen. I'll take a look at it, but until then I'd recommend taking a look at Weapon Sidegrade. That'll help you move over your attachments to the tier 2 weapons.

I have a save set before the upgrades (Because I was nervous if it would work) that I can reload if you'd like. I'm also running the game with console, log, and debug so I can load up, upgrade, and show you what the log says.

Don't worry, I'll try and figure it out. That said, an update likely won't come for a while. Shen's Last Gift came out and I kinda want the chance to play around. That and I haven't even gotten the chance to play around with my own mods either.

No worries, just wanted you to be aware. :) With Weapon Sidegrade, it basically solves it for me whilst you enjoy playing the game yourself. ^^

PS. Love the mod. Super addicted to it.

I appreciate it. =)

You have a good time as well friend.