Issue with TinyG Motor4/A axis

[CaptCrash]

I am at the point of connecting up the electronics to the TinyG controller and I have come across an issue that may be a faulty channel on the controller.

This is the first of the motors I have connected, it works intermittently on the Motor4 channel.
Initially the motor will turn (1-2 seconds), but then make a high pitched sound and stops turning.
My method of testing is to press the "Test A" button from within the Basic Setup screen of the Liteplacer software.

So far I have done the following
1. Initially I had the POT turned all the way to the left prior to connecting the stepper.
At this point the LED associated with the Motor4 channel is dimly lit (on initial power on it was as bright as the leds for Motors1-3).
Turned off the power and connected the stepper.
Turned on, connected and it makes a high pitched "I'm unhappy" sound.
I turned up the driver current and this did not change the result (It did change the volume of the sound and the brightness of the LED)

2. I moved the stepper to to Motor1 and then Motor3.
My method of testing is to press the "Home X", "Test X", "Home Z" or "Test Z" buttons as applicable from within the Basic Setup screen.
The stepper works as expected and confirms that the cabling and stepper appear to be fine.

3. I measured resistance for each of the cable pairs.
Between pairs on the same coil, there is approx 9.5 ohm of resistance.

I have not tried a different stepper motor on the Motor4 interface.
No other motors, limit switches etc are connected.

Does this sound like a faulty channel, or am I missing something?
Any help or suggestions would be appreciated.

[JuKu]

It sounds like there is resistance in turning the motor or it doesn't get enough current. Please check the mechanics without the belt, don't over tighten the belt and try lower speed and acceleration settings. Also, marginal connections can mean that the motor does not get enough current. You could also increase the current setting (turn pot clockwise), but moderately. Maximum current setting can burn the small motor, so watch out for motor overheating. Warm motor is ok, but you shouldn't burn your finger when touching it.

Of course, it is possible that the motor is faulty. If you don't get it to turn with reasonably speed, send me email with your address to replace it.

[CaptCrash]

Thanks for the suggestions.

I swapped the connections for the A and Z motors on the TinyG.
I got a similar response from the Z motor attached to the Motor4/A driver.

I did notice that the Acceleration/Speed for Motor4/A was set to an odd number.
Acc was about 50 and speed was 5160 (both numbers are approx from memory). This seemed backwards.

I clicked on Reset all to Build-in defaults

ran the "test A" and it worked with the Z motor.
I then switched back and it all looks like its working.