Rename your uploaded files with tokens from the media entity.
Use this to set media and file names to the provided alt text.
Configure temporary directory: Configuration > Media > File system > File (Field) Paths settings.
Override path in settings.php:$config['filefield_paths.settings']['temp_location'] = '../private/burndown';
In order to rename uploaded files, they are uploaded once with the original name, then converted on save. This can be a problem when you upload an image with a filename that already exists, in some cases uploading an image from your phone is always image.png.
The "Incorrect redirect hash generated" may be related, as the error message looks the same.
Bulk renaming files works well, just change the filename tokens and select the re-save option.