Sometimes when i or my users uploads a file to the Downloads and attaches screenshots to it, the upload fails and
the user who uploaded the file is displayed with this "rubbish" data:

Any idea what could be wrong and how to fix?

This is how the data looks when It´s encrypted.

20 minutes ago, jcdesign said:

This is how the data looks when It´s encrypted.

Any idea what could be the problem? .jpg uploads just fine.

Running the whole community on https://

I have no idea! Send a ticket to support team so they can look at this.