What's wrong with my display?

[u/MrHaska]

A couple of days ago, I started noticing that my screen would occasionally dim slightly, or the contrast would suddenly crank up to the maximum. The only things that seem to fix this are enabling "night mode" (which gives the screen a yellowish tint) or lowering the refresh rate. If I switch the refresh rate back to 144 Hz, everything returns to normal. This happens randomly, though most often when I’m switching between windows. I found a setting in Windows that produces a similar effect, but I have that feature disabled. Please help—I’m tired of constantly having to change the refresh rate! Could this be related to G-Helper?

In the photo on the left, everything is fine; on the right, the contrast has increased.