That’s what an independent BMW mechanic did to mine when it failed. Stuck the flap in the middle and disconnected the cables. Worked fine after that, no message on dash. Left it like it was when I traded it in.Remove the cables , which than makes it easy to work the flap back and forth with fingers . Flood the top spring with copper grease and massage grease into the bottom swivel . Eventually it’ll be like new .
Don’t turn ignition on whilst cables disconnected or may get a fault code . ( I can’t remember if it’ll self clear thereafter or not )