Zack, of the JerryRigEverything YouTube channel, bent an iPhone Duo backwards, and its inner screen didn't make it. The titanium body held at first. Then a permanent green line ran from the middle of the folding display out toward the frame. He kept bending, more lines appeared, and the screen stopped responding to touch.

Per Android Authority, the Galaxy Z Fold 8 Ultra's inner display also failed the same kind of test, and the Pixel 11 Pro Fold took structural damage. The standard Galaxy Z Fold 8 came through in one piece.

So the Duo's body can flex far enough to hurt the screen inside it. The video doesn't say why. A hinge that isn't stiff enough, grit trapped underneath, or some other weak point in the design would all fit what happened.

Earlier in the video, the folding screen took scratches at level 2 on the Mohs scale, with deeper grooves at level 3. Apple's matte nano-texture finish hides those marks while the screen is lit. They don't go away.

With dust and sand packed into the hinge, the Duo wouldn't close all the way, because the grit pushed back harder than the magnets that normally hold it shut. iFixit saw something similar when it coated a Duo in fluorescent powder before its teardown. Only a little got inside, but some of it reached the moving parts of the hinge and made them crunch.

Since launch, several owners have heard a crunch while opening or closing the phone, then found lines across the inner screen, some within hours of buying it. iFixit lined those reports up against a 3D model of the hinge built from CT scans, teardown footage and Apple's patents. The damage clusters where the gap for the display's flex cable meets the hinge's central support.

iFixit also modelled a support bar that doesn't drop far enough as the phone folds, which would press a stress point into the screen. It calls that a hypothesis, not a finding, and neither test pinned down what's breaking these screens.

Opening one up is easier than on any other foldable iFixit has scored. It gave the Duo a provisional 5 out of 10, its best mark for a folding phone, and the batteries come out fairly easily. Several other parts can be reached without taking the whole phone apart.

Out of coverage, a new inner screen costs $999, and the replaceable matte layer on top of it is $49 without AppleCare+.