[Support] Black rectangle often flashes randomly at the top of my screen during normal use. Any idea how to stop it?

Hey, friends! I have a weird issue that I'm hoping someone can suggest a fix for, cause I have searched all over and cannot find an answer.

Essentially, for the last several months, I randomly get these black flashes that happen at the top of my screen. They take up the top 1/4-1/3 of my display and they're gone in an instant. They happen at random times. Not while I'm gaming, but sometimes when I'm watching a non-fullscreen video, browsing the web, etc. I cannot purposefully trigger it, I have no clue what it is. The only thing I can think of is maybe it's krunner, because it's positioned similarly to the krunner search bar? I really have no clue.

It seems to pop up more often while I'm active (typing, scrolling, clicking, etc.) but not in any one particular program or at any particular time, and it definitely happens when I'm inactive, too. It's really hard to pin down what triggers it.

Specs:
OS: Fedora 38 (KDE Spin)
Display Server: X11 (but it happens on Wayland, too)
GPU: Nvidia GeForce RTX 2070 Super
CPU: AMD Ryzen 5 5600X

My system/software is fully up to date.

I'm always running OpenRGB, GWE, and Mullvad VPN in the background, and I often have Firefox, Element, and/or Steam open at any given time. I don't think it's any of those, but I'm including this info in case it could be, or if it's helpful.

Any advice is welcome! Thank you.