Hello,
I have experienced exactly the same thing. It was only after purchasing a new board that I noticed that the problem persisted. Changing my programming cable did the trick. Mine was rather long and the much shorter one I'm using now is working fine. I dont know why it took months for the problem to set in but this is what fixed it for me. (apologies if my response does not meet the standards of etiquette for the forum. I'm a noob)