Element or infinite switch?

Element on Kenmore cooktop went out. Had it replaced and now it won’t cycle off (“runaway”). Could it have been improperly installed? If infinite switch was cause of dead element, how can it now be heating up? Would appreciate quick reply as repairman(?) is coming back tomorrow. Many thanks.

Here’s a helpful video to figure that out.
Electric Range/Stove Repair: How To Troubleshoot and Repair Burner Elements And Switches - YouTube