We identified the issue with the world upload. Only a bunch of users are affected by this problem.
Unfortunately fixing this problem is a bigger task and we don't know yet when it is fixed.
In the meantime you can try to upload the map and let the process finish. Then wait 30min/1h, with a bit luck your world is there.
Thank you for the help. But i ended up finding another way of "fixing" it. Thank you for the help anyway!