Workflow issue: Multiple instances seem to be running even though they don't show in History List

Workflow: Multiple instances seem to be running even though they don't show in History List.

I have a SPD2007 workflow which will modify a field based on the "Modified By" field. This workflow is set on run on "Modified" or "Changed" events. I only need to get the initial Modify By person. And the workflow need to wait for other users to change another field, which seems to trigger the "Modify By" to be changed. It seems this would reset my initial value again which was based on the initial "Modified By".  So the value changes multiple times during the workflow. The history list didn't show multiple instances running or duplicate actions occurring.

Eventually I took care of the issue by putting a "Pause for 1 minute" behind each of the "Update Item" action.

It seem the workflow triggering run too fast before they could put a stop to it. Because the workflow ends immediately and the "Change" even still fires to some effect which trigger another workflow?

Giving some "Pause" time seems to stop the workfow from trasitioning into another state. Just my guess.