Apple Store workers are getting frustrated with the rampant iPhone battery flaw

A serious bug (or two) is causing iPhone batteries to malfunction, and Apple Stores are inundated with customer complaints, employees tell Business Insider.

Over the past few weeks, complaints have been mounting that something is causing iPhones to suddenly shut off with 30% battery.

In a statement posted to its Chinese website on Friday, Apple re-stated that the issue is a hardware issue, and that it only affects certain iPhone 6S devices. iPhones with qualifying serial numbers can be brought into an Apple Store for a free battery swap.

But technicians and Geniuses at Apple Stores tell Business Insider that the issue is very common, and that it seems to affect more models than just the 6S.

Apple has declined to comment several times to Business Insider about whether the issue may affect more devices than just the iPhone 6S.

Complaints at Apple Stores are rising

Apple Stores are now seeing large numbers of complaints from customers concerned about why their devices are malfunctioning, several store employees have told Business Insider.

An Apple Store "Genius" employee in Manhattan said that 80% of their cases are currently a result of the bug. It appears to be affecting more iPhone models than just the 6S, the employee said.

"We have been seeing a lot of customers for this particular issue, and I have personally dealt with the issue on not just the 6S, but the 6S Plus, which is not part of the program," according to one Apple Store manager in another part of the US. "I've also seen the issue a lot for batteries outside of the manufacturing date."

Another US-based Genius said that his store had placed 80 part orders for batteries after the replacement program was introduced, and there weren't enough batteries on hand when Apple first announced the program. "It really hasn't been that bad, to be honest," he told Business Insider.

A different Apple Store employee based in the U.S. told Business Insider that they do not believe the reports of battery failures are related to iOS, but, rather, they are caused by a hardware problem with the batteries (as Apple has stated). But even though the batteries fail and shut down when they get to about 30% charge, Apple's internal battery diagnostics tool still says the batteries are healthy, this employee said.

The employee also said they were getting several returns due to the battery issue, but had no guidance from Apple on how to fix the problem until recently, so they ended up replacing the phones instead of just the batteries in most cases.

Another longtime Apple Store employee said that customers frequently complain about battery issues after installing beta software or failing to install the newest version of iOS. "A lot of times it's older phones with consumed batteries or really old software," the person said.

One person who went to get his iPhone 6S fixed at an authorized Apple Service Provider in London was told the shop had a huge backlog of phones to fix, and couldn't even provide a date on when it might be able to fix theirs.

Two bugs

There is some debate about the cause of the problem. Apple says that it is related to "a battery component that was exposed to controlled ambient air longer than it should have been."

But some have pointed at a recent iOS 10.1 update that was pushed to people's iPhones. People with the problem - including several BI staffers whose phones are not covered by the replacement program - are seeing their battery drain abnormally fast and switching off around the 30% charge mark.

A Chinese government watchdog is also claiming that the 6s hardware issue is also affecting other devices, including the iPhone 6, the iPhone 6 Plus, and the iPhone 6s Plus. For now, it's not clear what the relationship is between the two issues.

Apple is replacing batteries in affected 6s devices free of charge, but it isn't talking about the apparent 10.1 bug. An Apple spokesperson declined repeated requests for comment on the 10.1 bug from Business Insider.

If you're having the issue, you can check if your device is covered under Apple's current replacement program and if it is, you can have your battery swapped at an Apple Store. Instructions are here.

If Apple says your phone is not eligible for a battery replacement but you are seeing the random shutdown bug, email kleswing@businessinsider.com.