[Milsurplus] Shaky Tuning

[CL in NC]

Any thoughts on the cause of shaky tuning on a BC348 where, as you tune through a steady carrier, the beat note jumps up and down in freq a couple hundred cycles.? More pronounced on the higher bands.  Could it be the backlash is not set right on the gears? 
Tune cap seems lubricated properly, no dry bearings, rotor ground contacts also seem like they are making good contact. The receiver was repaired by another person years ago.  I found bad bypass caps in the oscillator module,, tuning and tracking are just about perfect.

Charlie, W4MEC in NC