Wired Keyboard A1243 Shift Keys not Responding

Hi, both shift keys on my wired keyboard have suddenly stopped working. All other keys function correctly. Have tried the keyboard with another mac, with and without the USB extension cable, and multiple USB ports, and still the same issue. They are also the only 2 keys that do not respond in Keyboard Viewer. Have reset NVRAM which did nothing, but the fact that the keyboard behaves the same across multiple computers points to hardware.

Any ideas?