Clicking like that is most commonly from the battery pack dropping too many Volts under load.
To test the battery pack under load insert the multimeter probes into two of the charger port's holes and see if it reads the battery pack Voltage. If it does not then switch the probes around to different charger port holes until you get a Voltage reading.
Next turn the power switch on and give the bike full throttle while reading the Voltage of the battery pack on the multimeter. If the Voltage drop under 33 Volts during this test then the battery pack is old or worn out and needs to be replaced. A good 36 Volt battery pack will only drop around 1/2 to 2 Volts when under load.
Please let us know how it goes.