Mongo repair database "ERROR: error: exception cloning object in local.system.replset "
ReplSet configuration exists on many other members of that replica set.  You can safely drop the local db collections (you can even drop the whole DB but then you will just end up syncing from another replica and there is no point to repairing this entire DB).  So drop the troublesome collection - it will be recreated when the host rejoins its replica set.  The only local collection you need to keep will be the oplog.rs collection - this would allow this member to know where to start catching up for operations it misses while you are doing repairs.