Issue adding buttons in addition to a matrix display?

I am having difficulty adding GpIO push buttons in addition to a matrix. I have a Raspberry Pi 4 with an Adafruit Hat so I have plenty of pins open. However, when I wire up a button to any of the GPIO buttons I get this warning:

RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings

…and the button doesn’t work. If I start up a file that does not reference the matrix, it all works flawlessly.

Whyis this? Should I not be using RPi.GPIO as an additional import? Do I have to reference something else?

More thorough question here: pi 4 - RGB Matrix interfering with GPIO button - Raspberry Pi Stack Exchange

I’m using the image-viewer and Video-Viewer and some of the demos on my matrix, and I added Buttons to the GPIO 16, 20 and 21. They are used in different processes (and totally distinct languages) and so far it seems to work fine. Maybe this gives you some idea?

Here’s where I instantiate:

And this is my Button class:

I’m using the Pigpio npm module, it was the only npm module that would let me configure Pull-Up resistors and work in an Event-Style way.

Another quick check: do you run your script as root? Or does your user have the gpio group? (It should be a different error message if that’s the problem, but worth checking anyway.)