I subscribe gwene.com.stackexchange.tex from gnus.
The images includes in an article are displayed as a black rectangle. After a lot of time images can display as they should, but after emacs-restart the issue is back.
I try to open a downloaded png image with eww-open-file. Same result. My Emacs-version is GNU Emacs 26.1 (build 2, i686-pc-linux-gnu, GTK+ Version 3.24.0)
emacs -q makes no difference nor does Emacs25.
It must exist something which trigger the correct display, but I did not find it. I need some help!