Sorry, I don't have an answer for you, but a question instead.
Did the glass plate ever stay in place as it turned before it broke?
Ours gets out of the groove and comes off the little prongs. I just figured it was because it was a tiny little camper microwave. I have a hard time getting it back in place because I am vertically challanged, so I just wiggle it around and around after I cook anything. I am interested to see what responses you will get on this question.
This is not exactly an answer to the question above, just more of a FYI I suppose. It is possible that the reason the plate is slipping is because the turn table knob is worn. This is NOT a common problem, but it is possible. I just want to make sure that I make a few points for anyone reading this forum:
1. Always use the metal tray when cooking in convection mode or the 1/2 time mode.
2. Do NOT use the metal tray when cooking in the microwave mode.
3. It is best to use glass cookware in the convection and 1/2 time mode, you just set the glass cookware on top of the metal tray.
4. It is not advised to use metal pans or tin foil in the unit.
If you have any questions about using this unit, please do not hesitate to post on there. I have one of these units in my home and I use it every day to cook. Some things I have found out by trial and error, so they won't be posted in any manual. Please do not think any question is silly. I will be happy to answer all of them to the best of my knowledge. If do not know the answer I will find some one that does. Thank you.