possible to distro-sync from 4.10 to f18?

[Neal Becker]

After updating to 4.10 from kde-unstable, I want to go back to f18 stock 
(because DPMS is broken and I don't know how to fix it).

But yum distro-sync gives:

--> Finished Dependency Resolution
Error: Package: nepomuk-widgets-4.10.0-1.fc18.x86_64 (@kde-unstable)
           Requires: nepomuk-core-libs(x86-64) >= 4.10.0
           Removing: nepomuk-core-libs-4.10.0-1.fc18.x86_64 (@kde-unstable)
               nepomuk-core-libs(x86-64) = 4.10.0-1.fc18
           Downgraded By: nepomuk-core-libs-4.9.5-1.fc18.x86_64 (updates)
               nepomuk-core-libs(x86-64) = 4.9.5-1.fc18
           Available: nepomuk-core-libs-4.9.4-2.fc18.x86_64 (fedora)
               nepomuk-core-libs(x86-64) = 4.9.4-2.fc18
 You could try using --skip-broken to work around the problem