Advice on Staining an older deck

I am located in Nova Scotia near the coast, think Maine. Fully exposed to sun and weather in the summer and rain/snow/slush in the winter. I typically don't shovel the deck off in the winter other then to provide an emergency exit from the door that access it.

My issue is that after sanding the top of the deck with a palm sander last summer and applying Benjamin Moore Arbourcoat Solid stain to the deck it is flaking off in large chunks after just one winter.

I am looking for the best way to prep the deck from this point. The boards are in good shape and don't require replacement (no checks, cracking, mildewing, greening, etc.). From what I can tell they are simple pine deck boards that had never previously been treated or coated with anything. 

So far my plan of attack is to pressure wash (have access to a 6hp gas pressure washer) and sand of any remaining stain from last summer that is loose. I am wondering what (if anything) I should apply to the deck before I put more stain down?