It may be that sheet metal pieces expand when the heat is on and they rub together. Check where the burner cone fits into the rear duct.
I have run into this problem before.
I checked burner cone where it enters the duct, that wasn't it.
I would try replacing both rollers.
I will replace both rollers. Do I just replace the support rollers, or do I have to replace both rollers and the axles at the same time?