Bit of a late answer. I repair simple stuff like countertop appliances. I don’t use silicone a lot, just a dab of clear stuff to cover screws that hold meat slicer blades, or on screws that hold the blade of hand immersion mixers. I try to use silicone that has H1 and NSF on the label. I am more interested in trying to find affordable food safe grease for the occasional planetary mixer repair. It is very expensive and our company won’t spend the money for occasional repairs. You need it when you need it though. Also, I believe it is assumed the food has Incidental contact only.
Is this in a business, Dairy Queen? Make sure ceiling is clean and good condition, no oil or food spatter, carbonized food; waveguide may be dirty and food residues burning. Staff use something metal inside? May need to replace antenna. All else fails, call ACP like I do.