I've a DFR0523 peristaltic pump connected to a Raspberry Pi 5 using the DFR0566 Expansion HAT and driven from one of the PMW channels on the DFR0566.

The pump suddenly stopped working and now when I try and drive it, it moves very slightly and makes a high pitched whining noise, but the spindle doesn't turn.

I've a second DFR0523, and when I switch the broken one with the second one (so plugging it into the same channel, with the same cable, and running the same code), it works fine and the spindle rotates.

The first DFR0523 is therefore malfunctioning in some way. The spindle turns fine, so it doesn't appear to be a mechanical fault.

I'd love to be able to repair it if I can as I'd hate to see a nice motor go to waste. Can anyone suggest any ways I could work out what's wrong and repair it? Are there any particular common modes of failure of these types of motor?