iPhone 12 Pro touch screen issue

I have bought a refurbished iPhone 12 Pro (with iOS 18.1), and as soon as I turned it on to set it up I experienced a weird touch screen problem. Basically the right side of the screen was mostly unresponsive (so for example the letters P and L or the backspace key took way to much effort to function).

I checked here and saw more people had the same problem: so I restarted the phone, but nothing changed. I force restarted it: still the same issue. I also tried to "paint" the whole screen in the Notes app and there were definitely some glitches in the right side, so I thought this was a hardware problem, and not a bug.

I left the phone on my desk for a couple hours (didn't turn it off), then tried it again to show the keyboard glitch to my wife, and everything worked perfectly! Tried painting the whole screen again, and there were no issues.

My question is: I have like 30 days during which I can return the phone and be reimbursed (or even request a replacement). Should I be worried there's something wrong with the screen itself, or if the problem disappeared it just means it's a bug (even if it didn't go away right after force restarting it)? If this was a hardware problem, it wouldn't just fix itself, right?

Thanks in advance.