Yosemite Server Profile Manager breaks on host name change

A problem with Profile Manager on brand new clean install Mac Mini with Yosemite 10.10.3, Server 4.1.

Initial setup was to try Profile Manager with .local networking, only to discover that the network does not support Bonjour (a complex multi-VLAN school environment). Things kinda work with IP, but since iOS resolves the ip to Bonjour name, it can't enroll.

Deploy DNS and change hostname using the Server.app -> trying to enroll an iOS device ends up with "500 Internal server error".

This was written in the log:

{GetMDMACLFromUserAgentHeader (mdm_enroll.php:71)} OSX version 10.10.3

{LogException (common.php:488)} EXCEPTION: 500 Internal Server Error - Could not retrieve SCEP challenge.

Only thing that really fixes Profile Manager back to normal so far is complete clean install of the whole system. Easy now when just testing the settings, but a disaster when the Profile Manager is finally populated with 300+ iPads and a network change is needed...

Tried the clean install once and changing the hostname really is the thing that breaks the system.

I've tried destroying and recreating Open Directory Master, recreating system keychain, resetting Profile Manager to empty, removing Server.app and /Library/Server -folder. No help.

I haven't tried replacing the Server.app with fresh copy in the process or recreating the certificates, yet.