Error when dragging & dropping a file from a Cryptomator vault to a web browser window

Hi,
I'm using flatpaks for Cryptomator and Brave Browser. Whenever I drag a file from an unlocked Cryptomator vault and drop it inside a Brave browser tab, it doesn't work and there is a transport error message (which varies depending on the site I'm dropping the file to). E.g. this is how it looks like on Paperless web admin interface:

However, it happens for all sites. Atm my workaround is to copy the file to my home user's `Downloads` directory and then drag and drop it from there which works flawlessly every time. After the drag & drop I manually remove the file from my `Downloads` directory again. This is pretty annoying. Is there a way I can enable files being successfully dragged and dropped to a browser window directly from an unlocked Cryptomator vault?

Interestingly, dragging and dropping a file from an unlocked Cryptomator vault to the local file system works. I have Flatseal installed but couldn't find a setting which changes the behavior.