Greetings!
Even if you are having the problem on occasion, or even just once, send for the replacement knob anyway. This way it is taken care of, and it will never be a problem again. The empeg folks are very good at handling this, and it is worth the email.
I had this problem in my car once, and found it mildly annoying. I wrote in and received the replacement knob in days, postmarked the day I sent the email out. I didn't seem to have the problem anymore, so I just put it in my desk until I changed the faceplate on the empeg. I put the knob on then, as long as I had the old one off anyway.
The new knob feels slightly firmer - the O ring, I guess.
Paul G.
SN# 090000587 (40GB soon to be 96GB Smoke)
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Paul Grzelak
200GB with 48MB RAM, Illuminated Buttons and Digital Outputs