Has any one has experience to deal with this car rental in Orleans?

Sorry, can't help with the Sixt office at that location but, I have this entertaining story...

In October 2021 we used the Sixt rental depot near the Gare d'Orleans. At the start of the rental period they brought the car to the Orleans station. Very convenient.

About a week later I didn't allow ourselves enough time to drop it off in the correct location, about 10 minutes walk from the Orleans station. Instead, I parked it in a no parking zone at the station, left the keys on top of the drivers side tire and called the Sixt office from the train. The Sixt guy wasn't to happy about this arrangement and chastised me for parking it there, reminding me it could be either stolen or towed and I would be responsible.

I called the Sixt office about an hour later and they successfully recovered the vehicle. I was nailed a €30 fee, plus they had to fill it up, and another €14 fee for that on top of the fuel.

You were lucky. I once saw a guy at the Florence airport back when you could not enter the rental car lot if the public lot was full, just park his car in the no parking zone in front of the airport, slam his keys down on the rental desk and run for his plane. Always wondered how that went but sympathized. The Florence airport lot might take two hours to enter if public parking was full as you could not otherwise access the area at the back of the lot where rentals were returned. It was a truly bizarre and very Italian way of doing things.