Messages with file attachments fail

See previous update

This issue is now resolved, and all messages with files attached can now be send again.

We aim to deploy before mentioned fix tonight after office hours.
Confirmation will done tomorrow morning.

We have prepared a fix that should resolve this issue, but due to unforeseen circumstances, we cannot deploy this tonight as expected.
We are working on deploying as soon as possible.
We apologize for the inconvenience.

We are currently experiencing issues with attachments in messages. All messages containing attachments cannot be send at the moment.
We are investigating the issue.