Flashing mileage usually means one of the nodes (possiblly the instrument cluster) on the CAN network is not being recognised by the body computer. Carrying out the Proxy Alignment procedure usually resolves it, however if there's a problem with the CAN wiring between the cluster and the body computer, the PA procedure won't help.
My money is still on water inside the engine compartment fuse box as Peat says in post 3 above.
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