I AM a technician and I’m well-versed on combi-ovens. But, no experience on BKI’s. So I’m not your man.
Combi-ovens are complicated and can have numerous underlying issues besides the one you’re experiencing now. Just like a steamer, they’re high maintenance if you have poor water quality and no proper water treatment. Not that THAT is contributing to your immediate problem, but that can cause future problems on a regular basis.
I hope someone can step up and fulfill your request. You’re obviously in a tough spot.
FYI: BKI ovens are actually rebadged European products, made either by HOUNÖ or (as of 2012) GIORIK.