404 issue with images

[Jimmi08]

Hi, I noticed this with images (if they are missing)

you are caching
cid is f.e. site/e107_media/999/images/2019-06/preview_frontend_.png
and
entity type metatag_default
title page (meta tag valur) is "Error"

if I set redirection to the system not found page
cached URL is (at least it's only one, not one recored for each missing image)
/site/?route=system/error/404&type=routeError

Is this correct behaviour?
Thanks