What pen kit are you refering to?? Is this the Flat top pen, sometimes called the "American Classic". I could not find this on Rockler's website.
Rockler sells normally Berea products. If you mean the Flat top pens, you must make sure that the tube is clean inside before you assemble the top part of the pen. I run a "L" bit through it to clean out even the smallest amount of glue or so that could be inside it. Before I had sometimes the problem that the twist mechanism was very tough if not impossible to operate.
Also, it takes not too mcu pressure to press the two pen parts together. You may have a little over done here.
The pen can be easily dis-assembled, but you may ruin the twist mechanism when doing so. It goes as follows:
get a rod that fit inside the barrel from the centerband side
drill a hole in apiece of wood so that the brass thingy that is on the other end will clear (you must unscrew the finial and remove the clip). Set the top barrel on the piece of wood so that the brass thingy is centered on the hole and press with the rod the whole mechanism out the back end. I use an arbor press, but a drill press will work, too.
Clean out the brass tube with the "L" bit and remove the brass thingy from the twist mechanism. In about 50% of the cases I can re-use the twister, if not use anew one.
Also, with pressing the nib end too hard to a hard surface one may damage the nib. I had a batch of chrome nibs that were too tight due to excess plating. I used small number drill bits to open up the hole so the refill can retract again.
HTH
Rudy