Thread:Project:Support desk/Wiki migration from Debian 7 to Ubuntu 14.04 had strange effect/reply (2)

Ok it's me again. Since nobody seemed to have any idea where the cause is, it did what I had planned anyway: I upgraded mediawiki to the latest release. My first step was to upgrade from 1.22.8 to 1.22.9 which did NOT fix the 502 bad gateway error. So I then upgraded from 1.22.9 to 1.23.2 and VOILA -> NO bad gateway error and the special pages link as well as the file upload are now working. I made no other changes except for the upgrade.

Maybe this experience helps somebody else...