Oh, fixed it.
Whatever little pin or clip holds the upper center vent acctuator lever to the flapper was, well, gone. Small bolt, double nutted loose and it works again.
I closes quickly, opens slowly, I imagine the pods leaking? Looks like dash removal time...
I also replaced my two temp sensors with a pair from the boneyard, they ohm'd out a little more "cold natured" than mine. Setting of 26C now keeps it comfy again. For another week or two..
ONE DAY! If I stay in MB's, I WILL convert away from this auto junk.
One day.