How many updates (.msp files) are located on the BE server in .../Backup Exec/Agents/RAWSxx/Updates?
If the push installer tries to apply more than about 8 updates, it will fail.
Try move all updates before the last service pack to a temporary location. If the remaining files are less or equal 8, try the push again.
If there are more, split into groups of max. 8 files and only leave one group in the directory while trying to run the push wizard.
If that was successful, put the moved files back and run it again.
best regards
Dominik