I have found that if I figure out in exactly what order the fingers are playing the messy chords (i.e. like thinking OK, the third finger always comes down first) then often the problem will fix itself. If you know which finger(s) is the culprit, and you think about that finger playing at the exact time as the others, sometimes, the problem can be helped.
Otherwise, the problem is most likely to be hand position. If you find fingers 3,4 and 5 are lagging behind fingers 1 and 2 constantly, or the other way round, try moving your hand on an angle towards the lagging fingers and see what happens.
Another reason for messy chords can be the fact that one finger is playing on a black key and another is playing on a white key. Obviously, the white key finger has further to travel so you might play it a bit later. If this is the case, you need to find a way for the white key finger to get to the key sooner. There a few ways to do that but if you just think about the finger getting there sooner, you can oftentimes solve the problem without struggling too much.
Also, of course, in this piece the top notes have to sing out. When I learned this piece I think I made the wrists generally hover more over fingers 3, 4 and 5 so those notes came out more clearly.
And I seem to remember using way too much pedal in this one. I think you could use quite a bit (sorry I can't be more specific). I tend to use copious amounts of pedal in Beethoven slow movements and almost none in fast movements.