Setup issues: Page not found; Could not resolve host; Unknown error

[bbczeuz]

I found two issues during setup of the plugin on current icinga2 (2.13.1) and icingaweb2 (2.9.3, using Apache 2.4.6 on Centos7)

Issues

Page not found

After creating the SQL resource in icingaweb2, I tried to configure the dependency_plugin. It automatically redirects to
http://10.20.30.40/module/kickstart
instead of:
http://10.20.30.40/icingaweb2/dependency_plugin/module/kickstart
[I'm not 100% sure about the initial path, because after I succeeded in manually going to the correct page, the issue didn't happen anymore]

Could not resolve host; Unknown error

Just after I submit configuration settings, above message appears in red on the bottom of the screen.
Firefox Debugger says:

Status: 500 Internal Server Error

Any chance to debug this issue?