Becker AR4201 tuning problem

Occasionally when I try to change the MHz setting on my Becker AR4201
radio the radio tunes in the wrong direction. In particular, turning
the outer knob clockwise should increase the MHz but sometimes
decreases it (and this is not when it hits the maximum value, where
that would be normal).

Has anyone else ever had this problem, and even better, know the
solution?

Could a noisy power lead cause this? (I suspect I may have a less than
perfect connection on the power lead and am working to correct that.)

Thanks in advance for any help.

Martin