Keyboard randomly not recognised on boot or reboot

For a few weeks, the keyboard if oftentimes not recognized when I boot the Mac, or even on reboot. Out of the blue, however, it would be recognized and work properly on boot or reboot.

It is plugged in one of the USB ports on the back of my 27" Cinema Display together with my Wacom tablet. The tablet is always recognized and functioning using any of the display's 3 ports.

I tried plugging the keyboard to other ports of the display, but it does not change a thing. It is only recognized randomly.

I thought the keyboard may be faulty but it is recognized if I would plug it in any of the tower's USB ports. All the same, it is recognized if I plug it to my MscBook Pro.

I also happen to have another keyboard (same wired alu) and that one too experiences the same problem when plugged to the display.

I don't get it since my keyboard has always been plugged to the display and it's been working perfectly fine until recently.

I have tried repairing permissions (no errors), resetting NVRam as well as the SMC with no luck.

Rebooting with only the keyboard (no tablet) plugged to the display does not solve the problem.

Plugging my iPhone charger to the display always works —just like the tablet—, regardless of the port I use on the display.

So, the display's ports seem to work fine and the keyboard doesn't seem faulty either. I just do not understand what is going on???

It doesn't make sense.

I guess I could use a USB extension to plug the keyboard to one of the ports on the tower but not only is it not convenient considering my desk environment, it's also just denying the current problem.

Any help/advice would be welcome. Thanks.