ChrisH43272

I did a bit of testing and got a video showing how to reproduce the bug and fix a save that gets hit with it.
 
Copy of the video description:
To reproduce: Exit the game with a holster or double holster equipped and with tools or weapons on your hotbar. Upon reloading, the holster's positions on the hotbar will be swapped with the belt's, and errors being thrown from tools and weapons being in the "wrong" places will cause a massive FPS drop.
To resolve: Remove the items from the hotbar and unequip the holster. The FPS will visibly increase as each item is removed and stops throwing errors. You can then re-equip the holster to continue playing normally.
To avoid: Unequip the holster before quitting the game.

Same here.... Console is same error repeating.... referencing the HotBar..
 
What  I noticed in several save/load tests is this :
Loads fine :
Item on back, nothing in belt, NO HOLSTER
 
Loads fine :
Item on back, Item in belt (screwdriver), NO HOLSTER
 
Loads with massive lag :
Item on back, Item in belt (screwdriver), wearing holster (empty)
Thing is, upon load, the screwdriver is shown in the Holster slot, and the holster is empty...
 
Screwing around with it some more, after the first successful load without a holster, if I switch things around, and then wear the holster, it loads normally... even if I set it up exactly as it was when it loaded with lag issues...
 
First time I had this happen... not 100% but Iirc, I had items on back, belt, and holster...