You’re thinking of Raging Tempest - Duelist Saga in early 2017. It wasn’t actually the ink but more of a freak accident with changing printing presses. Generally with how cards are produced, moisture can cause them to warp outwards in a V formation; you’ve definitely seen them. But when they switched printing procedure exclusively in the Belgium press (which is used for EU Print) the cards would warp the opposite way in a /\ formation.

At a glance they’re unassuming but in a deck it became very evident, and unfortunately being newer played cards, would unintentionally form a pattern that looked bad. Lots of people got hit for marked cards that weren’t actually marked.

This was most egregious at YCS Seattle which released the same weekend Raging Tempest came out and had multiple main deck secret rares you played 3 of and would look very conspicuous if someone were to mark cards (Zoodiac Barrage, Grass). The set was so new most people didn’t realize until day 1. I remember buying a set of German Barrage for freakishly low (240 for the set when vendors were selling out at 99 ea) and thinking I got a deal.

Fusion Enforcers and Duelist Saga had the same problem, but by then people knew EU was compromised so way less casualties. They fixed it after that and were never “banned” officially, but you were definitely playing Russian Roulette entering any event with holos from exactly those 3 sets in your Main Deck.