if it is still under warranty, I would contact them for warranty claim.
If it is not, I would contact them for support
If they have poor support, I would open up the servo, take the circuit board out and take a look at the soldering of motor to the circuit board.
If the motor solder is ok, I would look at the solder of receiver wire and signal wire at the back of the receiver wire soldering

If it stops at the same spot every time I would say the potmeter but sometimes it can be the motor also.

Contact Protek Amain, They have great CS support, I would not recommend opening it up. Given them the chance to help you out. Is this one of the older Chad Bradley Grey 170T's?

Does it lock with the steering links removed and only the servo arm swinging by itself?
Just want to confirm there is no binding on the links that might be causing a brownout.

Same thing happen to my cheap jx servo. The reason to mine is the motor tab desolder. Its more like they didnt put enough solder on the motor tab. All i did is just add more solder to the tab.

My servo is a coreless servo, so it only has 2 tabs... Brushless has 3.
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​​​​If u are not used with soldering... I suggest you to contact your seller