I would #1 suggest playing with it a bit to see what it likes before trying to modify any part of it. Learning the tool is often more successful that new and unsuccessful user modifications.
From a machinist perspective this ugly part wouldn’t cut it but the primer does fall into the hole and has clearance enough to fall out on its own weight. Note the entrance looks like a drilled hole in a flat plate, no chamfer, radius or rounded “funnel” on the edge at all.
This video shows how I use the Vibraprime (the device Hornady copied when they made the one you have) Winchester primers.
At start up of the vibratory motor, I am pointed up, so primers are opposite the hole, :29 in.
At this point I am watching the hole they drop into the tube from and the corner they have to flow into, single file. My angle to the right is noticeably greater than my very shallow angle to and away from the hole.
The aggressive rate they are flowing in the direction of the tube, is requiring me to bring the flow to a halt and reverse them all. That’s the jerking motion I am making, from time to time. If you are a fisherman, kind of like you would work a “popper”. Take away is the single file and from one side of the corner, going in.
Would have been a better video on the filler itself had I slowed down and been more deliberate. I might have to get one out and do a better job on that part.