On the 6500 there is a Toner Filter, that is suppose to help with remove excess toner. The gaskets look pretty good. So that's not the problem.
It is a very good idea to try and vaccum and wipe around the inside of your Machine. There is always going to be some Toner around. But keeping it managed is a very good thing. And helps with Preventative Maintenance. (Not having to call the Technician so much).
When you are wiping be careful. There are very little springs that can come loose and cause a code. Wipe but be gentle.
This will also help you to see what your Machine is doing. So you can stay on top of it.