Desktop Uploader reset EXIF heading data

Hello folks,
I use a GoPro Hero 3 to capture images and my phone to log GPS trace (with OsmAnd).
I’m doing a lot of tests with mapillary_tools commands before contributing to avoid uploading bad content.

The last point to complete my setup is to set the heading (camera direction) for my pictures. I used the --interpolate_directions flag and I was trying to check if the generated datas was good. So I dropped my images in the Windows Desktop Uploader, and I was surprised to see there was no direction for my pictures on the map.

Then I checked the EXIF data and… the MAPCompassHeading had been erased on all images! There were filled before the Upload tool, though (data comparison here). Did I miss something?

On the web uploader, the heading seems not read too… How to be sure the MAPCompassHeading datas are good?