Welcome to the "Club." The filling system Tibaldi put in these fountain pens (actually, they were manufactured by Stipula) may be the worst filling system ever put into a high end pen. Once exposed to ink, they break down very quickly.
The best person in the world to take care of your pen is Maurizio Abrami. He has designed a metallic filling system specifically for the Iride. It is not very expensive and it works beautifully. He did mine in 2019. That pen has seen very extensive use since the repair and still works perfectly.
Yes, he is in Italy, but if you are going to do it, get it done right. There are good people in the USA but their solutions are not as good nor as reliable in the long term.
Maurizio does the work quickly and I found my interactions with him were a real pleasure. Feel free to use my name. Finally, full disclosure, I have no relationship with him other than a very pleased customer.
Good luck!
abrami@lazzaroni.net
https://www.lazzaronipenne.net/
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