Dear Maxi,
The problem is of the same names shared by more than 1 field in your pivot table because in XML you can not have same name for more than 1 field.
So, you may have noticed that if you have only 1 expression and only 1 dimension horizontally then it will export fine but as soon as you add more than 1 expression or 1 more dimension horizontally then it will rename the next same value for field and make one more field which will contain the original name of the field.
Then I believe you can not export it as a pivot when you create more than 1 column in your pivot with same value.
Hope it helps.
Regards,
Ashutosh
