Can't tell if keyboard is scuffed or it's something to do with Synapse.

I just got back from a 20 day break, hooked up my computer, plugged in my Deathadder and Blackwidow Chroma, worked fine for the first few minutes, and then the A key just stops working. I un-plugged the keyboard and plugged it back in again, and the A key worked perfectly fine, again for the first few minutes. I honestly can't tell if it's the keyboard that's broken or it's something on my computer, any help with figuring out what's wrong with it would be greatly appreciated.

Edit: I've found nothing in regards to this issue anywhere at all, only that it might be something to do with Synapse.