Google may be repeatedly retrying to notify our system about the same site donation payment(s) that weren't placed through our system, so they're generating an error for every attempt.
Check the Integration Issues console in the Tools section of your Google Checkout account's Merchant Center, and see if the errors all reference the same Order Number, if so, and that number matches up to a site donation payment that wasn't placed through E-junkie, you can just disregard those errors. Otherwise, feel free to send any affected Order Numbers to our support team, so we can ask Development to investigate further:
You may want to create a donation product in your E-junkie Seller Admin, using the "Let buyer edit price" setting to allow buyers to enter their preferred donation amount; with that setting enabled, you can also set a Min. Price (which donors cannot undercut) and a Suggested Price (which will pre-fill the editable price field when donors first add the donation item to their cart). Using a cart button for this item in place of any non-E-junkie donation button you may be using would prevent the sort of errors the latter buttons are causing for such donation payments.