Paypal Standard checkout issue

[Jessie111]

Our site is using the default Paypal Standard payment gateway in Virtuemart 3.0.3

When customer clicks the "Cancel and return to site" in paypal screen, it will clear the product in the cart and gives two errors, see attached.

Why it says "the product out of stock"? But the product is not sold.

Then if you refresh the page, it will just give a notice "You have cancelled your payment."

[alatak]

Hello
I am not able to reproduce your problem. Could you please give me
- the vm configuration of Action when a Product is Out of Stock
- status of paypal for Cancel transactions
- stock handling option for the status of paypal for Cancel transactions

[Jessie111]

Thanks for your reply. Before I got your reply, I was asked by the support  to upgrade the VM to latest version 3.0.6.2.  And we just enabled the paypal express checkout from backend.

But now we get different errors with version 3.0.6.2
When you add some products to cart, and  come to the Cart, it shows "No payment selected",  then once you select the "Paypal Express checkout" , whatever you  do next will redirect you to Paypal, like removing the product from cart, updating the quantity in the cart, checking the terms and conditions, or clicking the "Save" button next to the select a payment method section.   

And if you select the "paypal express checkout", then clear the only one product in the cart(just added one product to cart this time), it will show below error:

Notice
Product quantity successfully updated
An error occurred. The payment has not validated. Please choose another payment

Error
Programming error,Paypal expresscheckout: total sent is 0
Programming error,Paypal expresscheckout: total sent is 0

Please help. Thanks a million.

Hello
I am not able to reproduce your problem. Could you please give me
- the vm configuration of Action when a Product is Out of Stock
- status of paypal for Cancel transactions
- stock handling option for the status of paypal for Cancel transactions