It's very hard to read the serial number but I want to say it's 1A111975 (the last digit is very hard to read).

I see no metal shavings at the base of the drive motor.

I can be maintaining constant pressure on the spring-return joystick and it will still happen so something must be sensing the speed/joystick position and want to kick it into high gear (for whatever reason).



EDIT:
In terms of the batteries, we have cleaned the batteries and have an amazing charger for them. We perform maintenance on the batteries more than anything else in this shop. When we purchased the machine ~5 years ago, we swapped all the batteries from bran new ones and had our electrician install them (he is a VERY thorough guy).

We just checked the water (all cells were good) and did a gravity test (also good). We always clean the terminals and if there is corrosion, they are either changed or cleaned right away (stop usage). All connections are good and the batteries still hold quite a charge.