XV270P Screen Flickering Problem in Monitor

I bought a second XV270P to have a dual-monitor setup, and after a couple months of use with no problem, one of the monitors started flickering at the very bottom (basically the area of the taskbar), then it progressively got worse until it was just showing a 2- or 3-inch high black bar across the bottom of the screen at its rated refresh rate (165Hz). If I drop it to 144Hz, the bars will flicker or look different, and once I drop the refresh rate to 120Hz it works perfectly fine.

When I take a screen capture, it looks fine. So I figure the issue is with the display, not the picture it's trying to show me.

I've refreshed my GPU drivers and reset BIOS multiple times, I plugged the monitor into my motherboard's internal gpu and it didn't change so at this point I feel safe assuming it's the monitor. If it's broken then it's broken, I have a retailer warranty and should be able to switch it out, but I'm wondering if I'm missing something simple.

Any ideas? I've got an Intel CPU with an NVIDIA card.

{Thread was edited to add model name to the title}