Very annoying bug in the iOS router utility with my Surf SOHO Mk3. It has persisted through many updates and firmware revisions.
If you edit on the WAN connections drag the active connection to disabled and another connection to priority 1 and hit done only one of the edits will take place. So if I want to swap WAN connections I have to edit, drag current one to disabled, hit done, wait, hit edit again, drag desired connection to enabled and hit done again. Very tedious and confusing if not paying attention because it looks like you can do both edits in one shot, then when you hit done one of them reverts.
In the web interface its much easier, no edit or done, just drag and drop as much as you want and it takes it.