Hope this helps as I've had the same thing.
On magento github somebody suggested the following:
This issue seems to stem for the "Gift Wrapping" Section within
/Magento/vendor/paypal/module-braintree-core/Gateway/Request/Level23ProcessingDataBuilder.php
Commenting out lines 186-189 & 198-232 allows PayPal via Braintree to process without errors
Under Advanced Braintree Setttings "Send Cart Lines" Should be set to NO, if items are not being added to the mini-cart
Basically, quote out these lines:
$extensionAttributes = $order->getExtensionAttributes();
$gwBasePrice = $this->numberToString($extensionAttributes->getGwBasePrice(), 2);
$gwItemsBasePrice = $this->numberToString($extensionAttributes->getGwItemsBasePrice(), 2);
These
if ($gwBasePrice > 0) {
$gwBasePriceItems[] = [
'name' => 'Gift Wrapping for Order',
'kind' => TransactionLineItem::DEBIT,
'quantity' => 1.00,
'unitAmount' => $gwBasePrice,
'totalAmount' => $gwBasePrice
];
$lineItems = array_merge($lineItems, $gwBasePriceItems);
}
And these
if ($gwItemsBasePrice > 0) {
$gwItemsBasePriceItems[] = [
'name' => 'Gift Wrapping for Items',
'kind' => TransactionLineItem::DEBIT,
'quantity' => 1.00,
'unitAmount' => $gwItemsBasePrice,
'totalAmount' => $gwItemsBasePrice
];
$lineItems = array_merge($lineItems, $gwItemsBasePriceItems);
}
Someone also supplied a patch in the same page