In my case it turned out that the charging point itself(evbox) contained a software bug. After it was updated, no more issues appeared. This might be the case for other evboxes in the Amsterdam area.
I'm also based in the Netherlands and I'm also facing the same problem! My 12V battery drains when I'm using public charging stations based in the Amsterdam area. My dealer blames the charging stations as well but I just will not except this argument for other EV's like Teslas charge without...