[Elecraft] KX3 Knob Responsiveness

[n4cw at aol.com]

My old KX3 (S/N 763) is a great performer but I'm concerned about the "responsiveness" of the AF/RF Squelch encoder knob. The VFO (?) knobs (A and B) work great and the response to turns is immediate. If I turn the AF gain rapidly, the sound (and the numbers displayed as "AF xx") don't react in sync, especially if I turn it fast. If I turn the knob slowly, no problem. 
 
Is this a known problem with "older" KX3's? Should I consider replacing the AF/RF Squelch encoder? The recent posting for replacing the "VFO" B encoder prompted me to ask the "learned masses"...
 
73, Bert N4CW/K1IMI