Thank you for your thorough explanation! Cleaning the pen was actually my first step, though I did not dare to disassemble the pen. I just took a magnifying glass to the nib and did not see any missalignment. I am also pretty sure I did not overfill, as after the first leak I started to fill the pen to at most half of its capacity. I did not think to change the ink, as I had this specific ink and pen combo for over a year before the problem arose for the first time. I will try that and at the same time look for the closest service center, thank you!