Today I could pick an Economy Comfort seat as a FB Gold member for free. These seats changed to "FREE" at 72 hours before the scheduled departure time and everything worked perfectly in the KLM app.
However, since selecting my new seat, I've noticed that the KLM app and website are not letting me change the seat again! In the app it says "not available", and on the website the seat details are no longer clickable. Has anyone else experienced this??