OpenCart PayPal Standard Problem

My site works fairly well but I've been getting a lot of abandoned carts. Looking at the logs, I see this error: PP_STANDARD :: RECEIVER EMAIL MISMATCH! I understand that there's possibly some discrepancy between the store order total and paypal order total. I need this fixed and I have additional work for whoever can fix this very quickly and is familiar with the platform. If you need access to the opencart server, you'll need to be familiar with SSH as the site is hosted on Amazon AWS. I will provide the key and access credentials if required.