PayPal Standard Payment for Cancelled Order Received

We have had multiple instances now where orders are successfully being paid for with PayPal but the order notes say “order cancelled by customer. Order status changed from Pending payment to Cancelled”, “IPN payment completed”, and “Order status changed from Cancelled to Processing”. We then receive an email stating:

Payment for cancelled order?[NUMBER]?received
Order [NUMBER] has been marked paid by PayPal IPN, but was previously cancelled. Admin handling required.

This is seemingly random as most of our orders are correctly given the Order Status of “Processing” for physical orders or “Completed” for digital orders, but some – and the numbers are increasing – are initially marked as “Cancelled” only to change after the PayPal payment goes through. We use PayPal Standard to run the payment through our website.

Please assist.

The page I need help with: [log in to see the link]