Anyone else have issues with NAPA/Oreilly master cylinders?

Brake parts are cheap, don't you be. Use new.

Myself, I use DOT5 fluid. Many on here will trash talk it. But the system can't rust if the fluid can't absorb water. Which.......DOT3/4 does readily.

Harley used DOT 5 for over thirty years and I never had do anything to those brakes except hoses and shoes, and I worked on Harleys for a decade.