Yeah. There are definitely issues with pellets sticking... That metal is seriously rough. They should have enameled or powder coated the inside of the hopper.
Here's a picture of a stack of pellets on the long incline of my new ex6. I just wanted to see how much friction there is, after I started filling the hopper from that side and the pellets wouldn't flow down. (Second picture) These are fresh lumberjack pellets. Note how high above the edge I could stack the pellets without any cascading. Pulling pellets from the bottom of the pile, emulating the auger, didn't cause the pile to cascade down either.
Basically, the hopper, at least on the ex6, is terrible. The slope is way too shallow, combined with rough, unfinished metal. No wonder we're having feed problems.