Bug overview description.
As seen here and here, the site force adds non working and non removable urls into source fields based on direct image links.
here it adds "lei_feiyang.deviantart.com" and here it adds "inar_of_shilmista.deviantart.com"

What part(s) of the site page(s) are affected?
All post pages.

What is the expected behavior?
That only relevant links appear in source field. Not Broken ones.

What actual behavior is given instead?
There should not be non-working irrelevant links that cannot be removed.

Can you reproduce the bug every time?
yes

Looks like it's a problem with the artist's file names. They named them using underscores, even going as far as listing a different artist on that first one, which results in e621's system trying to link to incorrect pages.

Highly related/dublicate: forum #207030

Fixed in 8bbbab9, pending deploy.
inb4 it breaks

This is now deployed. Existing sources will need updating.