I hate to admit it but we still have a lot of these copiers out in the field. For the most part they run well. From time time to time I will get one that pulls developer, when you open the side door it is a mess. Some times it is the developer seal ,some times the side door warps and causes the transfer roller to short out. If that does not solve the problem tray the drum holder. Inspect the felt drum seals and the toner recovery seal. I think that over time they wear and cause problems. The drum holder has a life of 150k I think, but we never replaced them unless they were dropping toner on the paper. Replacing them has solved some of our problems.