In my experience processing brass with the Rollsizer, I encounter the same problem if I load the casefeeder with a lot of brass. Watching it intently, I noticed that with too much brass in the casefeeder, some of the brass doesn’t drop towards the bottom part of the bowl during operation. When this happens, some of these brass gets carried over the top and goes underneath the DA plate near the opening of the casefeeder.
After watching and learning from this, I decided to not put too much bras in the casefeeder. I only put about 200-300 at a time to prevent the brass from going underneath the plate.