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(Pocket-lint) - Samsung's recently-announced Galaxy Z Flip wants to bring folding phones to the masses with a fashionable format, reminiscent of the filip phones of a decade ago.

Folding phones have been a divisive issue, with many questioning whether they will have the durability to justify the cost. The launch of the original Galaxy Fold stumbled when people started peeling the surface of the display off - and it seems the new Galaxy Z Flip display might have some problems of its own.

The phone uses what Samsung calls an Infinity Flex display, a plastic OLED panel with an ultra thin glass layer on top, which is then, it seems, topped with another protective plastic layer. But we're not interested in the ultra thin glass, because as we reviewed Samsung's latest folding phone, we spotted damage under the display surface. 

Having used the phone for a couple of days, we spotted a rippling in the display - not the surface - but in that actual display material itself. It wasn't really noticeable until we got out in bright sunlight and looked at the display in standby, at which point it was more obvious. It's hard to capture on camera, because it's beneath the surface.

This is not something we've experienced with regular phones and it's not something we encountered in the Galaxy Fold, although our use of these devices was basically the same. Whatever caused this, it shouldn't be happening within 48 hours of getting a new device. 

We've approached Samsung for an explanation as to what this might be and are awaiting a response.

There are two things that we think might be happening here, but let's be clear, this is speculation. Firstly, this part of the display sits over where the Snapdragon 855+ is located. Having played Call of Duty Mobile we noticed that it got rather warm in this section of the phone. The bottom of the phone is basically all battery, while the top is where most of the hardware is located. 

Could this be heat damage on the display?

Secondly, if you're playing games in landscape, then this is where your controls are likely to be. In the case of Call of Duty Mobile, this is where your left thumb is, controlling the movement of your player.

Could this be damage caused by this repeated motion on that area of the display? Is it a combination of both factors? Did Call of Duty Mobile kill our Galaxy Z Flip display? 

Of course, this could be a manufacturing issue, it could be because we have one of the first Galaxy Z Flips to arrive - but it's certainly unexpected when we've been careful in our use of the phone. There's been no excessive force on the display, it's just been used in a way that we've used all other phones. 

It's important to point out that this "rippling" doesn't actually affect the display's performance - or hasn't over the time we've been using the phone. Play a movie and you can't see it, browse your social media and it's not a problem, but it does raise another query over the suitability of these types of displays in smartphones. 

The Samsung Galaxy Z Flip has got off to a better start than the Samsung Galaxy Fold did, but concerns have also been raised about Samsung's use of the term "glass". It was launched claiming to use "Ultra Thin Glass" to protect the display, but it was quickly revealed by Zach Nelson from JerryRigEverything that this protective layer was easily damaged. 

It appears that the Galaxy Z Flip ultra thin glass protection has a plastic layer on the top of it, so it's hardly the glass that you thought it might be. Samsung is, however, offering a display replacement service on the Z Flip. In the US that will cost you $119 and in the UK it's £99 and it's good to know that things can be repaired - but equally, on a £1300 phone, they shouldn't get damaged in 2 days.

We still think that the Galaxy Z Flip is a great device, but if you have one or are thinking of getting one, then it's worth looking slightly deeper than just on the surface of the display.

Writing by Chris Hall.