There was a longtime bug here where the system would come up with all sorts of obnoxious error messages when uploading an attachment of more than 1 MB.
That has been fixed.
I am aware that there is another problem at the moment, where the system sometimes runs very sluggishly.
Has anyone noticed this bug occurring during the day or early evening, or does it always seem to be late at night? I am only noticing it late at night.