I had the same multiple swap problem on 107, MUC-IAD, today. Went from an E+ aisle on a no-Polaris bird to 31E (yeek) on a Polaris bird, after I had checked in for my VIE-MUC flight on OS's website. Twitter support told me only the airport could change my seat, which was a lie--once I got to wi-fi, I was able to change using the OS check-in utility.