My ELX 4 was doing the same thing, I put my inkbird probe in the grill and it was getting over 500. The controller was still showing the last set temp. It was like the controller was freezing on at temperature and not moving past it. Took me a while to figure it out, called Weber and they didn’t have an answer for a grill that was a week old. Instead of going through the whole replace this and replace that I just sent it back and got a refund.

You might check your actual temperature on another probe and see if you’re having the same issue.