@IamMrsG
My oven was inoperable for OVER a year. Same thing, many service calls, and parts, I eventually called the national service office for the brand. Learned that though he advertised being a licensed service rep, the person was in no way affiliated with the brand, and was using parts from who knows where.
They sent a trained person who had it fixed within a week, removed all faux parts, and the company reimbursed the fees and parts for which I paid.
The person stated he was trained by the co. and had it on his invoices, card, web, sign, and truck. On the off chance that this might be an the case, I pass this along.
Good luck.
"Animals are not my whole world, but they have made my world whole" ~ Roger Caras