Hi there, I am looking for advice on how to improve my pen.

I have 2 of those, and 1 works perfectly, it’s even in my top pens right now. But the second one, can’t write a full sentence without getting dry and stopping.

I though that it was because after manufacturing, some oils was still present and making ink flow bad or something. I took the whole pen apart, down to the feed, and clean everything with warm water and a bit of soap. Re-assembled and lubricated the piston part and the grip section with the o-ring.

Nope, it worked a bit longer, but next day, dry and then won’t even start.

Now, I wonder where the issue can come from. I guess air can’t enter the barrel hence the ink can’t exit? Or is there a different explanation? (I could breath through the breather tube, so I am confident air can go through)

Has anyone encountered a similar issue and could give me some hints?
I can take pictures if needed.
Thanks for you help.