Sounds like a valve, not a burner. (and this IS the place for off-topic
Try removing all the *****, and check the orientation of the valve shutoff shafts. Are the flats all aligned? Or is one of them off by a bit? The valve should be closed, regardless of sticky condition of the burners.
For the burners, soak all the pieces in Easy-Off for a couple hours in the sink, then without rinsing, put them through the dishwasher on the pots/pans setting.
If you find a burner that won't shut off, you can cap it off with parts from Home Depot, and just not use that burner until it'* fixed. It is one burner, and you're renting?