(ad for merchant) Ad not shown ¦ Reason: Your ad shares a similar Display URL with a competing, higher ranking ad.
(ad for my product) Ad not shown ¦ Reason: Another ad in your account is showing for this keyword.
Something needs to be done about this.
I would guess thats whats happening. Your lower performing ad (your product) rarely shows ragardless of whether another affiliate is bumping you.