Strange motor issue... motherboard maybe?

I've searched these forums (and the rest of the internet!) and haven't found a smoking gun so hoping someone with a lot more experience than me will be able to point me in the right direction:

I've got a Geetech A20M and have come to use it after a couple of months sat idle. The bed has stopped moving along the y-axis.

The first time it tries to move (controlled via the control panel), it makes a very quiet "clunk" noise and then nothing. It works fine if I plug it into the x-axis socket on the motherboard. Swapping over the driver from x or z makes no difference - and the driver from y works fine in the x and z sockets.

I'm left thinking it must be the motherboard - I thought it was most likely a failed capacitor but they all look fine (and the caps in the three sockets all behave as you'd expect under a voltmeter).

Question 1: Does this problem sound familiar, if so is replacing the motherboard the right course of action?
Question 2: Should I go for an identical motherboard (a GT2560_v4.0) or should I replace it with something different? (assuming the rest of the components will just plug in of course - I'm not sure how much variation there is in motors, hotends etc)

Thank you :)