Adding line Break On didn't help (in fact, there was already Break On at the start of script).
It seemed it works well on faster PCs and W2K clients.
After updating new dat, reboot was required for Windows to update its registry and reload new dat.
Is there execution timing issue?

The reason why I add Sleep 3 was to get shutdown.exe to execute.
If I removed Sleep 3, the scripts end normal without executing shutdown or likely terminated.

I used sdat*.exe with "force and silent" option.
I haven't tried to add "reboot" option.
I prefer to control the reboot requirement at the end of script.

I am going to try bstyles suggestion too.
Appreciate further inputs.