Read a schedule task log, please help!

The shcedule task I  a few months ago work nicely

however this morning I noticed the task was completed only at the beginning and the process seems to stop.

I went to the application log, no error was listed from this process then I went to the schedule task log and see this:

(screen shot attached)

This process is scheduled to run at 5:45AM every morning once.

I noticed in column ThreadID, the task is listed as Scheduler-2

Looking at other ThreadIDs from yesterday or the day before, I see Scheduler-0, Scheduler-1 and from last Sunday it showed as Scheduler-3

What does it means???? I don't see any error at all, anywhere. What can I do to find out what's the problem was, any advice?