In a gazelle test instance, after uploading a file, if you delete it, you can not add one anymore.

In a test instance, in the Files section,
1 - upload a file. That works
2 - upload a second file. That works
3 - delete any of the file you have uploaded. That works
4 - try to add a new file. You are prompted to select a file but the file is not uploaded nor displayed

There is a work around, which is to reload the page