Interesting thing I notice. My Simbot that got over 1847 scraps lags the game whether I fry to click or even HOVER my mouse over inventor bench, while with other lower level Sim selected doesn't. From googled (although I suspectsd before) I figured it was the cause of four digit number of scraps my Sim got in a stack being the freezing problem, as the game somewhat incapable and programmed to bload with said information, not knowing how to handle and optimize.

So yeah, headsup - Don't have too many scraps in your inventory when inventing, lol.

A little too late. Inventory has always been an issue for the Sims 3. I remember I had over a thousand fruits and veggies inside the fridge in my old save and the game started getting unstable. I think I read it somewhere on old Nraas wikispaces that too many items in inventory (sims, family, fridge, nectar racks, workbench etc) would degrade the game's performance.