Yes, the issue is sporadic, affecting only some transactions but not others, which has made it challenging for us and PayPal to troubleshoot.

We and a few clients did some testing that -- at least as far as we could tell from our limited test-sample sizes at the times we tested -- seemed to suggest occurrence of the issue might correlate with the following conditions:

• Buyer chose to fund the payment from their PayPal account balance, rather than from a linked card or bank account;
  ...and/or...
• Buyer clicked a link on the PayPal checkout site to view available shipping methods, but then neglected to manually select the sole shipping method available there*, yet PayPal let them go ahead and finish checkout anyway.

*Since we can already offer a choice of shipping methods (if the seller sets those up) in our cart before checkout, we only transmit the buyer's sole selected shipping method and rate to PayPal checkout, so there's only ever one method/rate available there.

That said, we don't know if those tentative findings would remain consistent across a larger volume of transactions, or if those tests just happened to coincide with PayPal tweaking things at their end that may have caused those results only temporarily, as they remain cagey about discussing any particulars whatsoever. We have at least reported those findings to PayPal in our MTS ticket about the issue.

If you want to keep your own PayPal MTS ticket open in addition to ours, you could just followup on that to reference our own MTS case # 10167138, which has been escalated and is currently set to "On Hold - Internal" status pending further action or updates from PayPal.

Nothing new to report. Every time I followup on our MTS ticket to ask for a status update, they just say they're aware of the issue and have escalated it to their engineers who are working on a solution.

Interesting, this is the first we're hearing anything about "eJunkie not adapting to those changes as intended", assuming that's not just a buck-passing excuse. They certainly never informed us we needed to change or update anything, and our PayPal integration is still fully compliant with their current documentation for it.

@mbw - We'll followup on our own MTS ticket to inquire further about that with PayPal; what's your MTS case #, so we can reference that in our followup?

Thanks for that; I have now followed up on our own MTS Case # 10167138 accordingly.

Here's how PayPal MTS responded to my followup seeking clarification re: "adapting to changes as intended":

Our engineers have figured out the root cause of this issue that is caused by our system. They are currently working on a resolution to this issue. And I was not informed to have you make any changes in your integration. So you don't need to change anything at this time. If I have any further updates on the matter will let you know.

I followed up on our own MTS ticket to verify that this bug is indeed fixed. They replied Friday evening to clarify:

We have made the fix, but it is going out in the next release cycle which should be within the next week. We will restart the experiment and monitor after the release has finished to make sure things are working properly. Will let you know once it is done.

PayPal MTS has now confirmed the fix was rolled out to live production last night. Let us know if you encounter any problems going forward. Thanks again to everyone for your patience and cooperation in riding this out.