So, used my closer for the third or fourth time today. I was having some velocity consistency issues, so I took the entire engine apart this evening. Turns out that the coating (nickel?) on the ram shaft has been flaking off and was gunking up around the ram oring. I sanded off as much of the coating as I could so that I wouldn't have to worry it causing issues, then polished the steel shaft with 2000 grit automotive sandpaper. Also, rigged a bumper for the back cap with a thin piece of foam. Hopefully it will still shoot tomorrow and the bumper won't totally disintegrate right away (and will reduce the pinging).
Kind of annoying that the plating on the ram just flaked off after 2-3 cases. Hopefully, it didn't cause any damage. I'm pretty sure it was preventing the ram for cycling consistently.