Recently came across this issue on 0.16 and upgraded today to 0.19b with the issue still persisting on Owncloud - so could well be an owncloud issue but thought to check here first.
When images specifically are shared using the ‘share link’ check box, as below -
I get a 502 Bad Gateway from nginx on the link generated.
However I’ve used mail-in-a-box for over a year for my business without issue and it has been a dream to operate. So I’d like to thank Josh for that.