In the end, I asked them to cancel my account. It is an account with thousands of euros per month in net deposits over several years.
This is not the first time they have canceled bets and then refused to review them or provide a real reason.
Furthermore, I am proceeding to file a complaint with the European authorities
This wasn't the first time? Can you provide some sort of proof proving that this happened multiple times over time? This is a very serious allegation to be honest and it could affect their reputation quite badly within this forum and elsewhere.
Am not sure how well the European authorities can assist since it's an offshore crypto gambling site, but all the best.