Recently had a bug report from the Music desk, where a large (~9 MB) image triggered a Network error when attempting download in Twitterbug.

This happened for her and two others on the Music desk, but when we tried using a different image (same photo, smaller size of ~200 KB) the tool and download worked perfectly. They were using current Chrome (v67) and Firefox (v61).
Probably also relevant to Quotable, since that uses the same tooling.