(please ignore thread all plugin web interfaces redirect to https and post openmediavault-nzbget plugin - this here seems to be the reason for both problems)
I tried to disable https access to the web interface for testing purposes, but, alhough the webinterface at 443 is disabled, nginx redirects all requests to https://server:443.
This happended some time ago, could be related to a plugin, but I'm not sure. any ideas, at least to re-enable the web interface at 443 for now, but, mainly to get rid of this darn redirect?!