Vision Pro owners are posting near-identical reports of a crack appearing on the front glass of their headsets. None of them seem to know how it happened, either.

The issue was first spotted by MacRumors, and so far, there have been five separate Redditors who have posted about it in the r/VisionPro subreddit. What makes it curious is that all of the uploaded pictures appear to show vertical hairline cracks in the same exact area above the nose bridge. All the affected Redditors say they didn’t do anything obvious to cause the cracks, like dropping the device or storing it improperly. Reddit user @dornbirn claims that they polished the front glass, placed the soft cover on, packed it away in the case, and woke up to see the crack the next morning. Most of the other affected Redditors also noted they either stored their Vision Pros in cases or placed the soft cover on.

There’s some speculation that this may be a heating issue when charging the Vision Pro in the case or with the cover on. Others contend it might be a manufacturing problem with the glass or simply a design flaw that puts too much tension on that particular area.

It’s also unclear whether the hairline crack is merely a cosmetic issue, as it does seem to appear over a sensor but doesn’t obstruct any of the cameras. That said, repairing the Vision Pro is expensive. With Apple Care — which costs $500 for the Vision Pro — there’s a $299 deductible for damaging the cover glass. Without it, it’ll cost $799. @ContributionFar8997 wrote that they had visited the Apple Store and was told that they’d have to pay the deductible in order to get the crack fixed.

We don’t yet know how widespread this issue is, as reports seem limited to Reddit thus far. The Verge reached out to Apple to see if it’s aware of the issue but did not immediately receive a response.