WooCommerce / Paypal payment validation error

I am currently utilizing woocommerce within my managed wordpress platform (url: http://www.zappcomics.com) and on 6/14 orders after 10am began having Paypal validation errors where the payment didn’t match the gross. My flat rate shipping charge of $5 has not been captured on future orders since then. Payments are hitting my Paypal account but shipping is not being charged.

when looking at the logs this is what I’m seeing –

06-17-2016 @ 20:35:10 – Received valid response from PayPal
06-17-2016 @ 20:35:10 – Found order #2956
06-17-2016 @ 20:35:10 – Payment status: completed
06-17-2016 @ 20:35:10 – Payment error: Amounts do not match (gross 79.96)

What can I do to resolve this issue asap?

Thank you.

https://wordpress.org/plugins/woocommerce/