If you always dig to the same depth, and you don't grow any deep-rooted plants, over the years you can form a compacted layer that won't allow water to penetrate. Try double-digging the bed this winter and see if the problem goes away on its own.
With 59% sand, really you should be adding material to retain water, not to get rid of it. An "optimum" mix is something like 20% clay, 40% silt, 40% sand.
Of course when you double dig, you might find some material down there which isn't "soil" at all - e.g. plastic sheets and piles of bricks that the builders just buried to get rid of them. Near where I live in the UK, a neighbour discovered about 200 glass milk bottles buried under a lawn which wasn't growing properly. How they got there is hard to imagine!