Checked #5 value this morning, about 45 ...
So the evaporator temperature sensor is bad.
I suppose the sensor is causing a condition that cuts off the climate control unit, making it restart and having interrupted the blower in the meantime.
Wish I had realized this before spending the money replacing the blower regulator -- I suppose I was due for a new one afer 100k anyway.

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2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)