Was this really necessary? I'm glad your renderer is superior to mine, congratulations.
Yes it was. And no it is not superior. There was a point behind it which you probably would have seen if you wouldn't have gone on the defensive.
If something is difficult to understand just by reading the code, then solving any problems in it will get near impossible.Especially for an outsider. My point was more or less that the code should be refactored.
Now,you are running on 1.6 and I am not aware if there are any known bugs related to this. I don't remember any.
What I would do in your case is that I would simplify the problem area till we got a failsafe base line to test against. To simplify the code just remove functionality. (layers, depth, etc)
When it works we add it all back one by one till we find what actually broke it. Do it in atomic steps. The smaller the better.