Help with ONBAR restore

Hi, Every month end, I do a restore of our production instance on to a training instance. I use the onbar( nouhup onbar -r &) command to perform the restore. OmniBack is used for backing up..Almost every time I do this, the restore hangs after it restores the ROOTDBS. All other dbspaces are pending. There is no reads/writes happening on the instance(onstat -D output). Usually keep retrying the command. Occasionally, I also reboot the unix box. It works after I have tried after a few times. The last time I performed the restore, I tried to try something different. I killed all the onbar processes running on the system. The instance was still up and in fast recovery mode. I tried the onbar -RESTART command. Voila, the restore of the other dbspaces started right away and the restore completed successfully. I am curious to know why this restore process keeps hanging. Any assistance with this issues is highly appreciated. Thanks Denis K