Please find solutions below

1. This is paypal, not a bug. Add a prefix via PP settings in WooCommerce to get around this.
2. I will reopen and investigate this if someone can give us steps to reproduce. We need a clean way to reproduce it, so no other plugins enabled, nothing like W3 Total Cache (not even object caching, to be safe).
3. I am seeing duplicate order IDs and lost orders. We had a customer dispute a payment on Paypal because she didn’t get her order, but she was charged. Her order is not in our system, but the order # exists with a completely different customer, with a status of “cancelled”.We are using Paypal IPN. We see numerous orders show as paid in paypal, then the order gets cancelled in WooCommerce automatically.Not sure if this is the same issue as above, but we’re very concerned with the integrity of our system at this point.
4. Step 1, add one product with 1EURO price. Buy th eproduct via paypal. Go again in the shop and try to buy again the same product. After your browser transfers you to paypal interface, there is a message: This invoice has already been paid. For more information, please contact the merchant.”.