Wow, I'm genuinely kind of stunned that others aren't experiencing this problem. I'm not sure why it's just me.
I owned probably 20-30 Frixons over the years, purchased at various times, and nearly all of them had this problem.
The only constant (beside the human being using them) I can think of is that probably 75% of my writing was in Moleskine-brand journals, and maybe 25% on index cards.
Good question. It happened even with Frixions that never left my house (which is the majority of them) here in the northeast USA. 90F/33C+ days are not uncommon here in the summer, but the Frixion writing in my notebooks ever went "invisible", so I think we can rule out a heat issue.
The ink in most of the pens was still visible and hadn't gone "invisible", so I don't think it was working but laying down invisible ink. It felt like the balls in the ballpoints had locked up.
I owned probably 20-30 Frixons over the years, purchased at various times, and nearly all of them had this problem.
The only constant (beside the human being using them) I can think of is that probably 75% of my writing was in Moleskine-brand journals, and maybe 25% on index cards.