Periodic problems... then nothing

I have had my M20 installed for a few years now and they have saved me plenty. About 6 months ago they would periodically beep/false for no reason.

Then about a month ago, they would not beep when I turned them on. The light now instantly goes to green with no test period/beep. I have checked the voltage supply, thinking I had a short, but nothing seemed to fix the problem. Yesterday I had a dead battery (left radio on too long) BUT I noticed that the Blinder started normally each time I turned it on. This only lasted until I jump started the car.

Any ideas?