Media Brightcove plugin conflicting with Media Upload plugin

There seems to be a conflict between the Media plugin for Brightcove and the Media plugin Upload (file). When both are enabled for a file field, the Upload plugin is broken.

Step to reproduce:

1. install latest drupal (7.56)
2. install, enabled latest brightcove, brightcove_media, media, views,
3. Configure Brightcove (access to an account...)
4. Edit article content type: change the widget to "Media browser" and enable the browser plugins "Brightcove" and "Upload" (admin/structure/types/manage/article/fields/field_image)
5. Browse the article creation form (node/add/article):
6. Click browse on Image field
7. In the popup, tab "Upload", select a file and click
8. Click Next
9. in the next step: click Save BUG! "Please wait..." text briefly appears and disappears, nothing happen.

The popup won't closed.
The following message is written to log:
Notice: Undefined index: #ajax in ajax_form_callback() (line 395 of .../includes/ajax.inc).

The expected result is: close of the Popup, return to the main node edit form, uploaded file should appears attached to the image field.