Whats up my eNIGMA!
Kueppers shells are good, some of the main issues with coins getting stuck are the above.
Some shells are made just for certain coins - because Roy trys for a nice fit, in short, it isn't one size fits all.
As JPM said, the ding could make it snug - I am not sure if I would recommend buying a DVD mag to learn to fix a problem you shouldn't have...so I will share what I do.
Take a bill - place it over the coin you are trying to fit it in - place the shell on the coin with the bill in the middle. The bill allows for the shell to "expand" a little, and if the coin get stuck - just bull the bill taunt and the shell will pop off. Doing this a bit, will help deal with "tight shell" syndrome.
A good shell should fit snug, but not too snug - in other words, be able to roll the shelled coin across the fingers, but no so tight it doesn't fall out when the shell is being held by the sides.
Roy is a cool guy - if it is a manufacturing issue, he will fix it.
Hope the bill between coin and shell tip helps.
Peace out.