Thin wall problem and strange auto fix

Hi all

I have a problem of thin wall with my object, and if i try to fix the interface add weird volume on the suspect areas, i can't undestand the problem

https://www.shapeways.com/model/3dtools/3045108/0/25?check=4

any suggestions? thanks

You had one face with an invalid orientation.
Are the two side supposed to be the same? I have made both sides the same, if that's OK.
The size is very small. What size is it supposed to be?

Thank you so much, now it's working!

How did you found the invalid orientation?

I converted it to an Stl file and opened it in Netfabb.