It would be a big issue if the config was sync'd to the peer if both units have the same hostname. If the units have different hostnames and a UCS is loaded (or the config is sync'd) only the shared config is loaded. If both units have the same hostnames, then the entire config (including the base network config) will be loaded. The result would be that both units would try to answer for all of the same self IP addresses and all load balancing would potentially fail.
I'd suggest correcting the hostname configuration error as soon as possible and not sync'ing the config until that is done. Make sure to take current UCS backups once you fix the hostname error.
Aaron