(SOLVED) MAX7219 grid randomly flickering on powerup

I'm having an issue currently where upon powerup, my entire LED array using 2x MAX7219's is just a mess of random flashing lights. It is never the same flashing, always random sets coming on and off with no particular pattern at all.

Note that this only happens when using an AC to DC adapter on the Arduino. If I use USB from my laptop to power it, no issues whatsoever, works 100% flawlessly. Just for some reason using the adapter. I have checked the voltages and everything seems fine (~5.04v going in using an AC to USB adapter)

Only thing I can think is possibly noise due to AC current? I don't have a 9v battery laying around to test the VIN pin on the Arduino.

Thoughts? If its just noise I'm not that worried as I will be using DC power in the end anyway.

First post, sorry if this has been covered, I tried looking for it to no avail

I turned my house upside down trying to find a 9v battery, turns out my multimeter is powered by one. Used that, no flickering whatsoever. So it's just the noise in the line from the AC I would guess.

How old is the "wall wart"?

It is not uncommon for the capacitors to dry out and fail, which means you are feeding chopped DC into your device. Not many digital devices appreciate that.

Both are less than 6 months old. One is an adapter that I got for my Raspberry Pi, the other is an iPad charger. Both do the same thing, even if I plug the USB from the charger to the USB port on the Arduino. Does it on both Arduinos (UNO and Nano).

Now that I think about it though, since my project is going in my car, it will probably receive noise in there as well, moreso than from AC I would think.

I guess I will start by trying a different wall outlet, maybe I have bad wiring in my house (wouldn't surprise me).

If I use a voltage regulator (which I will be) that should take all of the noise out if there is any, correct?