Just to let you know that we have been using our 8000 several hours a day for 3 weeks, on bidirectional, with absolutely perfect results. This is not something that should be happening obviously.
Wish i could suggest something apart from the head alignment routine.
Our 5000 works perfectly too apart from not wanting to take Museo Max through the 'Tray'. Has anyone had any luck with solving this issue or is a call to Canon Support required?