Hi! I was having the same issue with some of our donations. I found it so odd that it wasn't happening to all of the transactions, so I dug deep and realized that as a non-profit, PayPal allows you to accept both donations and to sell products/collect payments. Apparently, we had two different QR codes floating around.. one that took people to our donation page, and the other that took them to a payment page. I had to go searching through all our material/website/social media/etc. to make sure that all QR codes were pointing to the donation page. That fixed the problem. I hope it's the same issue for you and this will help!

You can manage your donation links in Paypal - https://www.paypal.com/donate/buttons/manage