Bug when Smithers exercises for Mr Burns?
Yes, it also happens with the Legs&Louie joint task, and with the Comic Book Guy & Agnes joint task. It also happens a lot with the Rich Texan's Mechanical Bull task.
Forum Discussion
You can't go into the build menu while these tasks are going. It seems to happen when moving things in and out of your inventory. It also happens when buying and placing items, so you are better off starting these tasks and leaving your game until they are done.
