Glad it's not just me. It's always been slow doing upgrades, but the time taken gradually increases the longer I spend in the upgrade screen. My computer fans spin up to very high speed in the menu screens (they are fine in-game) and when the eventual hang/crash comes I can see that the game has eaten 25+ GB of memory.
I'd love to be able to just bulk upgrade a stack of weapons at a time, just to reduce the crash risk and not waste extra time reloading the game.

Yep, last 2 updates have been complete FUBAR. Weapon upgrades are worse than ever and the whole mod seems laggy af. Nice addition, though, that isn't working yet; separating upgrades via weapon type. But buggy.
Czolee needs to fix his mod.
Fingers crossed for joy!