It does sound like the starter is not holding the contacts closed. A possible test would be to disconnect the motor from the unit and connect a lamp in its place, you should be able to turn the lamp on and off with the buttons. That will prove if the contacts are being held closed, the lamp will not draw enough current to trip the over current protection.
I have had this happen and it was down to dust in the holding contacts, a quick blow out with my air line fixed it, compressors are very useful at times.
My tool kit is almost complete, only a few more to get.