Unable to logon to BPM Workspace

Yesterday I tried to test a demo bpm process with a few tasks. But I couldn't logon to the workspace. I couln't find an error, except for:

<[ServletContext@452818297[app:OracleBPMWorkspace module:/bpm/workspace path:null spec-version:3.1]] Servlet failed with an Exception java.lang.IllegalStateException: Response already committed

I tried several optional solutions, like setting the listen-address, that did not work. What solved the issue was setting the ServerURL in the System MBean browser of the soa-infra.
To do so in BPM12cR2, go to the Enterprise Manager, (eg. http://darlin-vce-db:7001/em as it is in my VM) and go to the soa-infra:

Then in the SOA Infrastructure -> Administration menu open the System MBean Browser:

In the System MBean Browser look for the Application Defined MBeans and expand it:

Within the Application Defined MBeans, expand 'oracle.as.soainfra.config', then your server  and then 'SoaInfraConfig' and click on soa-infra:

Find the attribute ServerURL and edit it to the host:port of your soa-server, including the 'http://' protocol, eg. 'http://darlin-vce-db:7005':

 

Don't forget to hit the enter key and click on Apply:

Restart your server and it should be good to go.