The easy thing to do is invest in an oven thermometer--or 3, check the readings & take that into account when you set the temp for your oven. (I had an oven that was about 25 degrees 'off' consistently so, if I needed 350 D, I always sat the oven at 325...)

If it's a new/ almost new machine (under warranty), then I'd call the Wolf factory or the service company & ask that a different tech person be sent out for another go.

You also need to call Wolf CS and speak to a MGR about the tech's unwillingness to make the repair as you want. You'l need ot do the tests ci recs, so you have empirical info to back up your story. I'd also try to undo the payment to the servicer if in fact your tests show his 2.99 thermometer is not accurate.