We have an ongoing critical issue with our live checkout page failing to successfully submit an order based on a phantom "Missing Shipping Option" -- even though a shipping option has clearly been selected (see screenshot below). None of the three available shipping options will allow a successful order submission. If it helps, we also make extensive use of multi-ship. Strangely, this problem is NOT an issue once multi-ship is triggered. It's ONLY happening when there is a single Ship To bucket.
Any clue as to how this is even possible and what the fix might be? It goes without saying that we'd love your assistance in getting this ironed out as soon as possible.