Why does WebDAV fail from inside home network

sorry for cross-posting from super-user.com.

I am running my own OSX server, and so far it has served me well. Roughly since I upgraded to OF2, I have issues with syncing while I am in my home network (the same network where the server resides).

What could be reasons – or particularly, how could I find out what the problem is? Is there a log in OF2 that could point me to reasons for a failing connection?

There is a section dedicated to local sync in the Omni server guide – should sync locally work different locally only? This does not seem to make sense for me… the server has a constant address (via a dynamic dns service)… the service works, because I’m able to connect from outside the network… could it be related to the host name and/or the computer name?

[edit:] Is it possible that this is related to a certificate issue?

Thanks for your help,