Will it be possible to "reconcile" domain controllers?

Question

Active Directory

Good afternoon Colleagues!
It so happened that in the Active Directory forest 2 controllers of the same domain ended up with slightly different operating systems:
Primary controller in the central office (DC) - Windows 2008 SP2 x86 (6.0.6002) - all FSMO roles
Secondary controller in the Chelyabinsk branch (DC-CHEL) - Windows 2008 R2 SP1 x64 (6.1.7601) - GC only
All this somehow worked for a while, until quite tangible problems with DNS resolution of domain hostnames began.
As I found out later, for some time (quite a long time) the controllers did not see each other, and DC-CHEL was most likely turned off. The DNS log had warning 4013 from the start, which was waiting for the primary directory sync to complete. And about a year later, it was replaced by error 4000, after which users felt something was wrong. We couldn't see any direct prerequisites in the system log. Indirectly, it may have affected: warning 29 from Kerberos-Key-Distribution-Center, and then, when error 4000 from DNS went, 1055 from GroupPolicy, 4 from Security-Kerberos rained down.
It is obvious that initially something interfered with replication. The controllers are in different sites and different subnets. Everything is fine in the TCP / IP stack, although there was one moment when there was no reverse route on the DC, but this was fixed.
I see several possible reasons:
1. Due to differences in Windows versions (R2 and non-R2), AD services cannot work correctly together.
2. DNS Warning 4013. Google leads to completely different topics. And the advice is also different. Up to the transfer of the DNS zone to a separate DNS server (not integrated into AD). So I didn't fully understand.
Perhaps I missed something. I'll add along the way, if anything.
What are the possible solutions:
1. Downgrading the role of the DC-CHEL controller (which is also not yet feasible in standard ways, dcpromo / forceRemoval does not help, gives the error "DFS Replication: The main end name is incorrect.") to a member server. Bringing controllers to one version of Windows.
2. If, nevertheless, the joint operation of these versions of Windows is possible, then somehow force them to replicate.

repadmin /replsum
Время запуска сводки по репликации: 2015-09-24 01:51:25

Начат сбор данных для сводки по репликации, подождите:
  .....
Исходный DSA        наиб. дельта     сбоев/всего %%   ошибка
 DC               >60 days            5 /   5  100  (2148074274) Главное конечное имя неверно.

Конечный DSA        наиб. дельта      сбои/всего %%   ошибка
 DC-CHEL          >60 days            5 /   5  100  (2148074274) Главное конечное имя неверно.

Возникли следующие ошибки при попытке получения сведений о репликации:
        8341 - dc.epa.net

In general, what do not do now with the DC-CHEL controller, everything depends on one error " The main end name is incorrect. " Can you suggest something more efficient with less labor, so that the controller does not have to be taken to reinstall Windows from Chelyabinsk, and then back .

Answer 1

So.
It has not been possible to reconcile. But after dancing with a tambourine, dcpromo / forceremoval did work. After cleaning all the metadata, I raised the RODC on it, which initially had to be done.

Answer 2

Different versions of Windows do not interfere with AD (the main thing is that the level of the forest and domain be equal to the highest version of the domain - in your case, Windows 2008).
Your problem is purely in replication. If one of the controllers could not replicate data from another for more than 180 days, this is sadness.
forum.oszone.net/thread-212829-4.html
Read here, a similar case.