Google's Pixel lineup might offer some of the best phones out there when it comes to software, but they've always struggled with one hardware issue or another over the years. From the Pixel 2 XL display to the Pixel 3's long list of problems, the reliability of Pixel devices isn't among their best selling points. Now it looks like the back panels of some Pixel 4 XL units are peeling off, but Google has promised to exchange devices still under warranty, refuting claims bloated batteries might be at fault.

Via reddit and Google's own support forums, a number of customers are reporting that the back panels on their Pixel 4 XL units are coming unglued, typically starting in one corner and worsening from there. It seems like the majority separate from the left side corners, but that may just be a coincidence.

While Google seems to be shipping out replacement devices to those affected, that doesn't necessarily solve things, since the refurbished phones sent out can also experience this problem. A Reddit comment last month from a user purporting to be the General Manager of a uBreakiFix store speculated that the peeling could be caused by a faulty connector that makes the phone's battery expand. They go on to say that it's a known issue behind-the-scenes.

In answers posted to Redditors, Google assures that the battery isn't the problem, though:

We’ve investigated the issue and concluded that this is not related to the Pixel battery. If you’re experiencing back glass lift on your Pixel 4/4XL, we recommend reaching out to 1:1 support to explore warranty options. We’re here to help and want to make sure your Pixel 4/4XL is operating properly.

Expanding batteries wouldn't be new to Google smartphones, though: a not-insignificant number of Nexus 6P owners experienced this kind of failure. While it's a problem that can afflict any smartphone, a pattern of such failures isn't a good sign, and tends to lend itself to the narrative that Google's phones just aren't as well-engineered as they could be.

Updated to include Google's statement on Reddit.