I've had one for 2 years now and only had one problem. I must admit that after the first use, I saw some flaws in the design and set out to fix them.
The first mod was to forget the small vinyl tube couplers and attach a Dillon pickup tube end to the tube. This required a little sanding to reduce the tube outer diameter just slightly.
Next, to take the top off the tray to load primers it must first be removed from the handle. To do that you must remove the tube. All this (dis)assembly was bound to cause excessive wear and problems at the tray to feed tube interface. It was also an annoyance. Using a rotary tool, small burr, and hobby knife I opened up the top of the handle to allow removal of the tray top with out disassembly. Now I simply remove the try top, clamp the tool between my legs, slide open a pack of primers in the tray, shake if necessary, and replace the tray top. Much less hassle and no wear on any parts.
I also placed a piece of opaque tape in the center of the tray top to remind me to remove it before loading the primers. I won't mention what I said just before this idea came to me.
Another design flaw IMHO is that the tray is square. I believe that if the tray corners were not exactly 90deg, the primers might feed smoother with less "rocking" of the tool required to keep them moving. There's definitely and art to finding the right angle and motion to make the primers flow smoothly.
In something like 20k rounds I've never experienced a upside down primer. I've used only small CCI primers. I watch each as it drops into the tube and can see some try to turn sideways or jam at the opening, but with a little rocking of the tool they always right themselves. If I see brass as the primer drops, all is good. I've yet to need to dump the tube because I saw silver as the primer dropped in. The color difference with CCI primers is a distinct advantage.
The one problem I've had was a "defective" primer just this week. It had a burr on the rim of the cup and jammed in the tube.
Overall, I'm very satisfied with the tool, but the design could use some work.
---Scott.