I haven't heard issues with clapping or ocean noises, I used U571 for ocean noises and parts of LOTR - FOTR for various clapping noises also listened more closely to Eagles Farewell tour in DTS and they sound great to me. I am suspecting you may have a bad 663, maybe time left for some warranty or exchange for another make?

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70