This condition, which is characterized by a sudden change in tuning from one station to another, for no apparent reason, can be traced to some defect in the oscillator circuit. In the majority of cases it will be found that the tuning condenser assembly must be replaced. Loose rivets, which hold the bakelite insulating panels on the side of the tuning condenser sections, are usually the cause. These rivets are used for contact purposes, and the intermittent condition is produced by faulty contacts at this point. [I would think replacing the loose rivet(s) with a screw and nut would be a reliable fix here. CS]
From the Philco Serviceman – March, 1935.