K,

Based on your description,

I would agree with you, and the need for a thermostat.

You may want to check for loose wires and proper voltage to the wall oven,

But other than that, there's not much you can do ... most if not all of the repair parts for your machine have been discontinued by the manufacturer.

Were it me, I'd start thinking about a new oven.

Sorry, about that.

Good Luck,
:) :) :)