The high voltage head that rides on the drum appears to be not charging the drum surface where that is happening. You see the text fade out and come back. Is this head part of the drum assembly or does it come down from above on the lid to the drum/toner cartridge area? If you are lucky it just needs to be cleaned with a q-tip and some rubbing alcohol, although it could be a dead spot in the high voltage head which applies the charge to the drum for the toner to stick to. They make cleaning wipes for these heads which are basically a packet with a wipe soaked in rubbing alcohol. But a q-tip and small amount of rubbing alcohol might remove something that made its way and coated this head with.
