Hello,
i am having 3 problems with restoring two DC's from production into my lab environment.
I would like to reach a situation where i, as STEP I, can restore the FSMO holder DC to a standalone running, functional state. It is ok if it runs standalone only for a week (TSL not exceeded). During that week, as STEP II, i will then restore the second DC.

Both DC are Server 2012R2 @ Forest,Domain FL "Windows Server 2008".
Both DC are in the same site, but in different subnets (connected via a transparent router).
Both DC are holding GC and DNS role.
Images from Production are taken via "wbadmin start backup /allcritical".
I will call these machines FSMO_DC and OTHER_DC here.

After restoring only FSMO_DC from Image, i *might* not be able do start dsa.msc (NAMING CONFIGURATION NOT ACCESSIBLE) until i set the BurFlags to D4 and restart the File Replication Service.
Now i can start dsa.msc, but creating new objects is refused with "Windows cannot create the object because the Directory Service was unable to allocate a relative identifier", so i am hitting KB822053 here.

To fix that, i restored OTHER_DC from image (which i wanted to avoid), went back to FSMO_DC and forced replication with repadmin SyncAll /Ade, resulting in a FSMO_DC accepting new objects.

Signing on to OTHER_DC and running repadmin SyncAll /Ade failes with "-2146893022: The target principal name is incorrect", hitting KB2090913.
running \\FSMO_DC on OTHER_DC failes, running \\OTHER_DC on FSMO_DC is ok.
running \\ip.of.FSMO_DC as well as running \\FSMO_DC.fully.quallified.domain on OTHER_DC is ok.
DNS on both machines is able to resolve both machines for a) short hostname and b) fqdn, forward and reverse.
I temporarily fixed that by adding an additional NIC to OTHER_DC wired to the same subnet as FSMO_DC is in. \\FSMO_DC is working now and replication started immideately at OTHER_DC.

I feel that there is a Netbios Name Service issue here and need help to understand how that works.
No LMHOST files or WINS Servers are used.
So why is FSMO_DC able to run \\OTHER_DC without problems, but \\FSMO_DC can not be resolved from OTHER_DC ?

Any idea to avoid all of that trouble and reach my goal of a standalone running FSMO_DC more easily ?