[Elecraft] Strange behavior when tuning around with SUB receiver LINKED

[William Evans]

Looks like I may not be sticking to my explanation after all.  Try  
this and see what you get:
WITHOUT the SUB Receiver linked, tune the main receiver to 6.000.000  
MHz.  Be sure you can see the frequency of the Sub Receiver on VFO B  
area and the tuning rate is FINE.
Push A>B twice to synchronize the two VFOs.
Now tune the main receiver to 5.999.999 MHz.  You should hear a slight  
click.
Look at the frequency of VFO B.
Mine read 5.346.50 while the main receiver still read 5.999.999
Now tune back to 6.000000 on the Main Receiver.
Both VFOs on my K3 read 6.000.000
mmmmm...... something fishy here!

Any explanations, anyone?

Bill
W4ISH