atmega328 glitching on and off

It does cause more ripple that's why I pointed out that the input filter had to be bigger and in this case since there is a linear regulator the added ripple makes no difference . Even with a 470uF instead if the 2200 uF min I had mentioned the ripple could Never be big enough to cause the regulator to even be close to it's dropout voltage. You will remember that the original issue was the reg shutting down because of overvoltage... So I listed several different workable strategies to fix that problem.

Doc