Fix Duplicate Order Issue on Woocommerce due to timeout at checkout -- 2

Due to last freelancer conning us saying it fixed when wasn't fixed and already paid him then blocked us when sent following up message looking for help!. Project reposted sadly! Please be advised this project milestone will not be released for 3 weeks after completion in order to verify it fixed. Sadly due to one bad freelancer it will be 3 week milestone as we can't afford to pay someone to not fix it! We have urgent issue where we are getting dupe order issues across 2 different sites. Will it mainly happening on credit cards it also looks like it happening on paypal too (most of our order credit card)! The issue is where it's timing out at checkout, looking like it not processed order, not shown order confirmed screen but it has created the order. Customer then ordering second/third and even fourth time. In most cases it's creating order in Woocommerce backend but not creating/sending the invoice to customer so customer is unaware of the order. We then end up refunding large volume of duplicate orders! I believe this is something very similar to (fixing this should fix papyal): [login to view URL] Need someone who has knowledge of fixing these not first timer!