[codefox1]

Sure seems like slippage. Let's see, at 1450 tuning gang would be almost fully open. I would try spraying a little WD-40 in a cup and apply a tiny amount with a toothpick on the bushings or bearings of the tuning capacitor as well as any other ancillary pulley bushings. I would also check to see if the dial cord spring is giving some tension to the cord. Dial cords sometimes stretch, and sometimes there are 2 or 3 holes provided for the spring's anchor to increase tension for just this purpose. Yes, a bit of rosin rubbed into the string might help, but it would probably be temporary. Some just bite the bullet and restring. While doing so, the control shaft area where there the string is wound on would have to be cleaned up really well, maybe even roughed up a little with very fine sand paper to provide a little "tooth" for the string.

I assume the dial indicator is not hanging up the mechanism, but to be thorough, check it too.