See e.g.
https://gitlab.tails.boum.org/tails/tails/-/issues/17367
The attachment links in the Attachment section work fine. However, the links in the comments where they were added have bad URLs:
https://redmine.tails.boum.org/code/attachments/download/2547/GNOME+Settings+Selection.png
It should be:
https://redmine.tails.boum.org/code/attachments/download/2547/GNOME%20Settings%20Selection.png
Also, why not point to the static Redmine archive directly? You will have to eventually. :)
BTW, I noticed that the static Redmine pages lack an attachments section in the description. The attachments can still be found and accessed via the comments they were added in, however. Example:
https://public-redmine-archive.tails.boum.org/code/issues/17367/