Looking at our logs I am seeing failed responses this past week, and the checkout id's appear associated with draft orders. However, I'm noticing that in the response your correctly echoing back the x_reference id which is associated to a checkout record tied to a draft order. What API are you using to get the checkout details?
Would you mind running a new test, attempting to complete a draft order with your payment provider and providing the date and time in UTC of that request. It will help me and our payment team in our troubleshooting efforts.