I had a NVFR student have a vac. pump failure when we were on the last leg of a NVFR navex, towards the end of his training. I let him continue to fly & manage the problem, with the view that I'd take over if needed.
Then when I did his test some days later (with a new vac pump installed), the poor sod had the AI fail. Same as before, I let him deal with it. Fortunately we'd met all the required test items. He did fine so I passed him.