The problem as I see it is that Manager follows the ideal scenario โ as you describe โ even when the situation is less than ideal.
That could be a solution, but the warning system should be persistent, meaning not just a single alert before posting but instead something more nagging like a banner or a status or something.
Also, the unintentional effects of the original entry should be corrected after the user makes necessary adjustments. You can see this post to know what I mean by unintentional effects: