自定义折扣,PayPal实际扣款并没有计算实际折扣

自定义折扣的代码,主要按照https://www.mageplaza.com/devdocs/how-add-custom-discount-magento-2.html写的.

核心代码为:

 public function collect(
        MagentoQuoteModelQuote $quote,
        MagentoQuoteApiDataShippingAssignmentInterface $shippingAssignment,
        MagentoQuoteModelQuoteAddressTotal $total
    ){
        parent::collect($quote, $shippingAssignment, $total);
        //按等级折扣
        $info = SansiLocalHelperCustomer::getCache($quote->getCustomerId());
        $discount = array_get($info, 'discount', 1);
        $level = array_get($info, 'level');
        if($discount != 1){
            if($level > 0){
                $label = 'Sansi Level' . $level;
            }else{
                $label = 'First Order';
            }
            //在现有折后总价上，继续打折
            $sansiDiscount = round($total->getSubtotalWithDiscount() * (1 - $discount), 2);
            $discountCurrency = $this->_priceCurrency->convert($sansiDiscount);
            $total->addTotalAmount($label, -$discountCurrency);
            $total->addBaseTotalAmount($label, -$sansiDiscount);
            $total->setBaseGrandTotal($total->getBaseGrandTotal() - $sansiDiscount);
            $quote->setCustomDiscount(-$discountCurrency);
            $discountAmount = $total->getDiscountAmount() - $sansiDiscount;
            $label = $total->getDiscountDescription() ? $total->getDiscountDescription().', '.$label : $label;
            $total->setDiscountDescription($label);
            $total->setDiscountAmount($discountAmount);
        }
        return $this;
    }

实际效果,前端页面上按客户等级,出现了折扣:

支付后,后台查看预付款状态下的订单:

后台点击invoice,此处结算未计算自定义折扣:

点击 submit Invoice,实际收款后,订单实际支付金额为折扣前金额:

这个问题,上线前没有测出来,所以现在很抓狂.请各位大佬赐教.