No, that's an old bug...{ahem}...feature. At least I dealt with it a lot on 6.0 and probably earlier. When you save a scheduled agent you clear out the record on the server that the scheduled agent has run today, and it puts the agent back in the queue.
The workaround I adopted was to change the scheduled agent to a hidden manual agent. Then I would create another scheduled agent that runs the hidden manual one. You can then edit the manual agent as much as you'd like without triggering it when you save.
Here's the generic code I'd use in the scheduled agent. Just change the name of the agent and this should work for you:
Sub Initialize
Dim s As New NotesSession
Dim db As NotesDatabase
Dim agt As NotesAgent
Set db = s.CurrentDatabase
Set agt = db.GetAgent("(Send Reminders)")
Call agt.Run()
End Sub
UPDATE:
If you have access to the server, you can add a setting to the Notes.ini to prevent this behavior:
Amgr_SkipPriorDailyScheduledRuns=1