Scheduled Tasks not getting executed

[systron]

After we upgraded 7.6.1 We are facing issue of Scheduled task not getting executed, what I noticed that when you repair or reboot its very much executed for once but as soon as once SWsoft\Plesk\admin\AutoUpdate\PleskUpdater.exe scheduled executed we gets messages of though that scheduled tasks were perfomed but in real they simply cease to get executed with a very unique code :

Ended with code 128 : Tue Aug 15 00:00:002006

thing worth looking is :

Code 128 : Perhaps some one knows or plesk may know.

as one gets succesfull we recive this message instead:

Ended successfully:

I expect some one has answer for this.