Control Power 20 may be a 2 amp power supply. If that is the case, it may be as mentioned above, the power supply is not quite capable of running these locos. Many of the older locos draw 2 amps or a little more. Cleaning and lubing the motors so all runs freely does help reduce the load a little but probably enough.
That behavior certainly seems like the breaker on the power may be going in and out.
The locos would draw a bit more under load also.
