Well, to put a stamp on this...I tried various different methods over the past few days. Some involving heating and other ideas. I also tried sulfuric acid. First 30 minutes, then 2 hrs, and just now I pulled it out after 18 hours heated. Nothing.
As can be seen form some the old posts that were linked above, the issue appears to be the glass. And, best I can tell, if it is polished/resurfaced, it will not be very good.
I spoke to a very helpful person at TNR. She was passing my issue along to their support group who was to get back to me with either a solution or cost of a new element and installation. Unfortunately, it has been a week and I have not heard anything. I will follow up again.
have you tried muriatic acid?
i used it to clean hazed 100 year old windows at our old house. they were behind ancient bug screens and not washed for decades and nothing budged the mystery haze which we theorized was mineral build up from rain. at the suggestion of a hs chemistry teacher we used muriatic acid mixed with distilled water and it took it off so they looked like new.
i do not recall the concentration but he started with a very low ratio and kept adding acid until it worked.
some dimly recalled tips keeping in mind i am not a chemist! no recourse!
1. always put the water in the jar before the acid to avoid offgassing. also, the water ratio is key. muriatic acid will not work alone.
2. use a paint brush to work the acid solution on the glass. when you have it right there was a chemical reaction where it forms a froth as you work it in and the haze just vanishes.
3. rinse it first with distlled water and bicarbonate to neutralize the acid, then again with straight distilled water. we used two spray bottles to rinse and wiped that off with two cloths. most times it took two or three rounds of applications to fully clear the glass.