Jacks have been known to fail with an increase in load during a wheel change. I've seen it happen and it is a PITA trying to sort it out especially if it's nose wheels. It is good airmanship to pause/hold refuelling and cargo loading if the job can't be completed before. Passengers can usually be permitted, depends on type. When lowering off the Jack after completion I would usually ask that boarding is stopped so there are no trips at the door threshold as the airbridge or steps adjust.