Hello Aniket, thanks for the quick answer.

I checked, and those nodes are indeed midside nodes. 

I tried exporting my data with Multiple Object Export, and it worked quite well.

There is still one issue though, since the exported data are all sticked together (values are separated by a coma), and not well separated as expected and shown in the documentation. 

Do you have any solution to get a well formated document ? Here are screenshots of my file and of the expected format of the documentation. 

Thanks a lot.