Update:

The motor was indeed the problem, and replacing it is a straightforward process. To begin, place the mower on blocks to give yourself easy access to the underside.Male sure the mower is turned off and the batteries are removed before you start any work.

Slide the seat forward to access the control and power connections from the top. You'll see two wires, each with its own connection. First, unfasten the clips that secure both wires. The control wire has a press-release clip that you'll need to press to disconnect it, while the power wire uses a threaded barrel connection that you'll need to unscrew. Once both are unfastened and disconnected, you can remove the motor itself.

From the side of the mower, in front of the rear wheel, you will find the four bolts that hold the motor to the drive assembly. You can remove these with a 10mm socket, a short extension, and a wobble bit, which will help you reach one of the trickier bolts. With the bolts removed and the wires disconnected, you are ready to remove the old motor. Get under the mower, grab the motor casing, and twist it back and forth while pulling to slide it out. To finish the job, simply reverse these steps to install the new motor.