It's unclear what exactly happened. I would advise you to contact customer service directly to speak to an NS employee about this. They can correct this and give you a refund. This can be done by phone; they are available 24/7 at 030-751 51 55. You may also contact them by chat (click the link Chat with NS on this page) or by sending a message on X (formerly Twitter) or Facebook.

Seems like you checked out at Woerden at 16:37 and then decided to leave the station on the other side at 16:41 without checking in again?

This is an error because the gates on the other side should let you out without charge (already checked out) but I’m not 100% sure about that.

The 20 euros were not withdrawn from your bank account but from the balance on your card. See https://www.uitcheckgemist.nl/?locale=en but they will probably point you to NS Customer Service anyway.

And then NS somehow made four registrations out of that second check out?

For 6 October, I only see one incomplete registration with costs.

After checking in at Utrecht (16:00) a train ride was made to Woerden
If that was with the 16:25 sprinter, arrival at Woerden is 16:35
This fully explains the check-out at 16:37 (at normal cost)

What happened between that time and the 16:41 checkout needs to be investigated, it looks like some double check-out (with origin of travel unknown), or a 4-minute passage through the station.

No big deal, but of course the € 20,00 should be waived. The upper two transactions for 6 October at Woerden clearly indicate a ‘station passage’, and should be free. Same as the 3-minute passage on 30 October, which is correctly registered.