SIXT (MUC) problem
 

It came out that they gave luxury selection car without sufficient adBlue and car blocked its engine in 200km. The car was specially checked by agent before handing over.
Sixt is not taking any claim.
Would need a help, how to act
DM etc, any tips

Call sixt and state your case. Otherwise drive to the closes Sixt station and have them have a look. Or fill the car up with adBlue and keep the receipt and hand it in for reimbursement.

Whatever you do ... don't let this small problem ruin your day.

I had the AdBlue go low on mine during my 2 week E220d rental in Munich. I simply filled it up and kept the receipt. When I returned I was re-reimbursed for the exact amount.
I think the car goes into limp mode if it has no AdBlue.

i had no idea of that it was missing. the engine just "got locked" and they had to pull the car away. And gave me an alternative car, not same category and billed for it as well