Drop Down Progress Line

Mike,
The zig-zag progress lines will be vertical and will have no zigs and no zags provided that everything that has been done is in the past and everything that remains to be done is planned to be in the future.
If the progress lines have zigs and zags, it indicates that something is wrong or that something to do with the updating which should have been done (such as moving planned tasks into the future) has not been done.
Other than this, the progress lines are pretty much useless. They do not indicate tasks which are ahead of schedule or behind schedule. They are just a sort of artifact which were only ever included in the software because someone (I’ve heard it was someone in Japan) asked MS to put them into early versions and they have just stayed there.

Try setting on Tools/Options/Calculatio(tab) to Edits to total task % complete by selecting the check box and re-schedule the job.

Edits to total task % complete will be spread to the status date Distributes the changes to total percent complete evenly across the schedule to the project status date (status date: A date that you set [rather than the current date] for reporting the time, cost, or performance condition of a project.) (or to the current date if you have not specified a project status date). For example, if you are updating tasks to 100 complete complete, you can view the incremental progress on your tasks for a specific range of time.

Clear the check box to distribute the task percentage of completion changes to the end of the actual duration of the task. By default, this check box is cleared.

Let me know, I am not sure if it will work.