Feeling a 'click' in my clutch pedal

[SBSerpent]

Only appears after I have driven the car for a bit - say 30 minutes - in stop and go city traffic. Also, I only feel it on the pedal return. I've checked the clevis, made sure all fasteners are tight, including the two mounting bolts for the master cylinder and have greased the linkage associated with the pedal. Looking more closely, I am suspecting the push rod where it fits into the socket that pushes the piston in the master cylinder. Gonna try pressing some grease into the ball and socket connection to see if that corrects the 'click'. Any other ideas? Otherwise, the clutch operates just fine. Good pedal feel and good clutch engagement. All original 2011 build with only 4400 miles on the car. Bone stock. Fluid is original.