I have. Px 850. It does exactly the same thing. On grand piano 1 when I play the e or f below middle c, there is a loud clicking sound on the right speaker. If you play either of these notes loud it doesn’t happen It only happens if you play with a little less than full force. If you change the main voice to bright piano it doesn’t happen. I bought one of these instruments for a friend and took the opportunity while I had it to exchange the main board. It went away. Is there anything else I can do other than changing the main board. I love my px 850 but this means I can’t play it A new board costs over $300 I believe. Help !