Certificate enrollment for Local system failed to enroll Event ID:13

I've just finished installing a second domain controller to gain redundancy in the network. (and to solve some issues) After installation and configuring all errors are gone but one that is:

Event Id 13: Certificate enrollment for Local system failed to enroll for a DomainController certificate with request ID N/A from [CA NAME] (The RPC server is unavailable. 0x800706ba (WIN32: 1722)).

The first DC has the ECA installed. That action caused some problems I asked about in this thread and was the trigger for installing the second DC.

Normally its not to hard to find a solution for an error with a well-known event id. But Google for this error gives me a lot of different solution so I thought it might be a better idea to ask here hoping someone recognises the problem.

Edit: Left the server alone for the weekend because I heard that certificate propagation can sometimes be slow in starting up / functioning properly. Today I noticed that certificate enrolment was working without changing anything. I'm going to monitor it to see if it keeps working.