I have been having a similar problem, in my brand new save game post Nifty Knitting install. My Sim has the Knitting aspiration, lives with her cat in her Nifty inspired Cottage. A cache clear and new TS4 folders didn't resolve the problem.
Yes, with the knitting basket constantly in her inventory, she would stop doing everything and anything to knit. Even in the bath, though there was no animation, just both Icons together in her actions.
I worked out that taking the basket out of the inventory might stop her constantly knitting and starting new projects - 2 pies full of projects to resume! I realised this when she was supposed to be making a garden salad and finished a knitting project! Even though, again, there was no knitting action.
But she was also taking several in game hours to eat! An hour to make a single serving of Fruit Salad and 2 to eat it, and that was with cancelling queued actions, like pet the cat, and after I had removed her knitting basket!
So, I saved the household, saved the lot and started a complete new save game - OK she lost her friendships, items on Plopsy, inventory items etc, but, although only one test, she made her salad in 1/2 an hour and ate it in 20 mins! I'm cautious as she hasn't done any knitting yet but I'm keeping my fingers crossed.
