We have two 5100E's. Fortunately ours came with 4 year warranties.
Both of ours had the same problem you describe. Changed all filters and problem continued. There is a computer problem that each had. It was fixed under warranty either way. With yours, it will probably be covered because apparently this is a frequent problem, some kind of computer thing. And something to do with switching some hoses, trying to remember. Will ask husband when he gets home from work.