Image doesn't show in mirrored media gallery if added after mod edited another user's post

[azzurro]

Affected version

2.2.16 Patch 2

I don't recall seeing this issue before 2.2.16.

Steps to reproduce.

1. Create a post with an image as forum attachment. The image correctly shows in the "Forum Attachments" media gallery.
2. Another user (likely mod) edits the post and deletes the image, then adds another one (tested with the same one) as a forum attachment. The post looks correct but the image does not appear in the "Forum Attachments" media gallery.

Edit:

I set up "Forum Attachments" with the option:

Mirror attachments from forums