Raised beds not draining
 

I have turned my old veg patch into five raised beds.
But when it rains or I water it they do not drain and large pools of water
remain on the surface.
Strangely though if I poke a cane in (and it easily goes in two feet, )
then, whoosh the water runs out leaving a hole.
It seems to be well balanced soil, clay/sand/humus.
It was a veg patch for at least twenty years, it had tons of horse manure on
a few years back and was double dug and more farmyard manure added before
being raised.
Any thoughts?

TIA
Slatts