HELP! ‘Your payment was successful but order was NOT created,please contact us’. Except,the order is created, customer places duplicate second order

I am using Magento 2.3.3
Recently, we are having daily issues with some customers where they place an order, enter payment details and then get directed to an empty cart with error message ‘Your payment was successful but order was NOT created, please contact us : No such entity with customerId =’
They are confused by this and then place a second order.
In actual fact, both orders have now gone through Opayo and both orders have been created in Magento so they have been charged twice.
So they then contact us and we have to void a transaction and close one of the orders. Can anyone help with why this might be happening? Seems to be every day since about a week ago.
Thanks,