I have to agree with @analyticshops on this.
We run clean shops with minimal plugins and all PayPal express plugins have issues.
This issue is because the user does not have enough funds in the PayPal account to pay for the order and the 10486 error should direct the user back to the original website to try another payment method. All which in theory should be done at PayPal rather than direct back to the website to try another payment method.
I believe 10486 error / way its integrated has now been replaced so is obsolete. PayPal express Plugins still use this old method hence the error appearing daily on most of our shops.
SEE HERE…
Important: This integration method is deprecated as of January 1, 2017. PayPal continues to support existing merchants using this method, but please be advised new features and enhancements will not be applied to these integration. For new integrations, see (Redirect for an alternate funding source)
If anyone from this plugin is watching. Can you look the error up at PayPal Dev and update the plugin to enable the newer (Redirect for an alternate funding source)
https://developer.paypal.com/docs/checkout/#redirect-for-an-alternate-funding-source