I got an AliExpress case with the typical rubber plastic case glued to a flip case (where I can put all my ID/credit cards and some bills and the magical emerngcy balloon).
But when I hold the phone, I guess there is pressure somewhere around it, and the phone makes a vibrating signal. Not just continuous, but like if it was doing one action (let's say activating the flash or something), but sometimes if I hold it too tight, it will so a few of those.
With the included case from the box, it doesn't do that, perhaps because it's not touching all sides.
I used the double back tap to take screenshot, but it wasn't reliable with a case (not even the included one), and I could just do the three finger screenshot, so I disabled that, so that can't be.