I was startled by this weird behavior in Job Monitor, and it took me a little while to realize nothing was actually wrong. I would call this a "minor usability issue".
I had Backup Exec open to Job Monitor to watch a job's progress, and all of a sudden the active job disappeared from the list. At first I thought the job had completed. But then I then realized the list had merely scrolled down a little bit without any action on my part.
I scrolled back up to see the running job, but every time, the list would jump down again after a little while. After a few iterations of this, I realized that Job Monitor had selected a job from the list automatically when I opened it. This job was far enough down in the list that it and the running job couldn't display in the window at the same time. Every time Backup Exec updated the running job's byte count, it would also scroll the window to make the selected job visible. Selecting the running job in the list made this behavior go away. (Selecting the other job made it come back).
I can fully understand the issue you are describing, however I am wondering you are seeing this behavior because you have selected the "Storage" as the sort order.
I am not saying that this is wrong in anyway but normally the sort order is either name; state, start time or end time of the jobs which then most likely will keep the jobs in the order you expect.