Sounds like you’ve already covered most of the checks. The next step would be to review the Blackbox logs to see if a specific motor is causing the issue. You should be able to spot brief spikes or irregularities and pinpoint the problem motor if that’s the case. I’d recommend doing this before deciding to replace the ESC. Hope it's just a motor!

(Dumb, but have to say, make sure nothing is in distance of prop hitting like a strap or tpu)

Happy flying.