DA trigger pull Stacking bad

[bigfish]

Just as the title says, in one of my Shadows the DA trigger pull is gradually getting heavier to the point that it’s pretty heavy right before the hammer falls, not the kind of rolling break that it used to have.  The gun has some miles on it and I have an identical gun that doesn’t feel anything like this in DA. Both guns are CZC shadows with the CZC fitted short reset disco. When taking the gun apart I can’t visually see anything wrong other then some wear in the side of the trigger shoe from contact with the frame. The only things I have ever changed on the gun are the trigger return springs and I installed a CGW floating trigger pin. Any ideas what could be causing this issue?

[ck1]

Long-shot guessing here, but: maybe something is wonky with your hammer-spring and/or strut..? ...the Tanfoglio guys have to play around with their hammer-springs and struts a bunch because Tanfo's kind of stack by-design in DA due to their short hammer-springs... since CZ's and Tanfo's are pretty much cousins, maybe check there? 

[jripper]

I'm thinking hammer spring.  Or maybe it's really dirty.  If it looks grimy you might do a full detail strip and clean.