PayPal issue - Payment done but no order generated

[justkeepcoding]

Hello, 
I have had a couple of issues with PayPal payments in my store. The client makes the payment using PayPal but they don't get a confirmation email, no order is generated on our side, yet the payment goes through into our account. 
First time:
Error message was: "This transaction couldn't be completed. Please redirect your customer to PayPal" Status: "Failure",

Yet the payment was done.

Second time:
Error message was: "Internal Error:

 Status: "Failure"

Yet the payment was done.

Third time:

I have nothing, no errors, no order, no recording of payment except for the Reference from PayPal provided by the customer. 

I've contacted Shopify and they've said it's PayPal. I've contacted PayPal and they've said it was Shopify first and the customer's fault after. I'm in the blame game.

I've had this issue happen for three customers in the last two weeks. Did it happen to anyone? Do you have anyway I can troubleshoot this?

Thank you very much!!!