due to schema changes, you can’t export/import Native XML files between different major OJS versions (OJS 3.2 to 3.3 won’t work). This is so for your second case.
For the first case (3.3.0-14 to 3.3.0-15) that should be possible. You can click on the red dot right to the “Resultados” tab to see what error happened.
If it can help, the “white error” of your first page appear every time I import our generated content, but the article and info are correctly imported. You might find your articles under “archived” with the wrong or missing issue. Good luck!