I just encountered this at LAX. Rented a BMW 330i. It had over 40k miles but was in decent shape, with one noticeable ding which I took a picture of before driving off the lot. Returned the vehicle in same condition as rented. 100% confident there was no additional damage. Sixt associate did a careful walk-around when I returned it, and noted no problems. So off we go to the airport.

Did not receive a rental receipt and the authorization fell off my credit card (CSP). A week or so later I get an email from Sixt Claims, asserting there was a new dent and two new paint-deep scratches. I was asked to fill out a webform. I did so, stating that "I did not damage the vehicle" and "The vehicle was returned in the same condition rented." Silence in response.

Today, two weeks post-rental, I finally received an emailed rental receipt showing no extra charges, with the rental charge going through on my card at the reserved price. I'm hoping this indicates that Sixt has realized it has no legitimate claim for vehicle damage. But if they pursue this, I will absolutely go full litigator with them (even though Chase insurance will presumably cover any claim for damage).

An exceptionally sleazy business practice. In decades and hundreds of rentals from National, not once has National ever attempted to pull anything like this.

I've already canceled one Sixt reservation and do not plan to ever rent from them again.