I had the same problem last night with one I just got second hand. I pulled the shell plate and cleaned out all of the gunk under and around the shell plate. A friend told me to lube with moly powder as it does not attract any residue. Since then I reloaded 300 rounds without a hitch...
I just put a HIVIZ on my 629-6, same sight. I chucked a drift pin in my drill press and turned it down using two files. I went to 3/100 under the pin diameter and I had no problem removing the pin.
FYI MidwayUSA has the same sight at a somewhat cheaper price. I also ordered the #54 drill and...