Apple's latest iOS update, 10.1.1 promises, among other things, "stability improvements and bug fixes." But some believe it's also carrying a new battery bug.

According to a report by PCMag.com the update is unexpectedly draining iPhone batteries. There's also an active discussion on Apple's own support site where customers are reporting iPhone 6 and iPhone 5S devices unable to last a full day without charging. Others report iPhones dying with "30 to 50% charge left."

Might want to wait on this one. Image: Apple

The report comes just a week after Apple agreed to replace the batteries on a small number of iPhone 6s devices that were prematurely losing steam.

Some users who have opted into Apple's open beta program report that version 10.1.1 (14B150) solves the problem (others, said it didn't help), but most iPhone users are not running beta software on their phones. The beta program is now offering version 10.2. Some in the forum have opted to roll back to a previous iOS version. One user on the Apple support forum reported that a rollback didn't help, either. Said JimS-in-Seattle:

Don't waste your time on rolling back to 10.1. I unfortunately confirmed faysal22's comment that 10.1 does not work. My phone is lasting about 3 hours now. Instead of the battery shutting down at 70% it is now shutting down at 85%. I cannot tell you how many calls I have been bumped from. BTW, when it happens my phone is essentially dead for about 10 minutes before I can use it again.

In addition to early shutdowns and rapid battery drain, others in a Hacker News forum reported that the Battery Consumption numbers given in Apple's Battery Percentage Table seemed way off. "Varying apps are listed as huge battery sucks even when I don't think they are (Calculator anybody?!?)," noted one frustrated user.

There are many reasons batteries in iPhones can appear to malfunction. Over-heating can impact battery life and performance. Background activity like mailbox synchronization can drain batteries, as can active social apps like Snapchat and Twitter. Repeated drops can impact the connection to the battery so that it never fully charges. There's also the fairly common issue of the lightning port becoming clogged with lint, making it impossible for the lighting plug to fully seat in the port (clean it out with a pin or toothpick). It's always worth checking all these things before assuming that an iOS update is responsible.

I've seen my iPhone 6 unexpectedly drop from 60% charge to 0%, even on iOS 10. After plugging it back into the charger, it almost immediately jumped back up to 60%. These glitches are, apparently, sometimes caused by an errant app or some sort of crossed signal inside the phone.

On the other hand, Apple has been known to release a buggy iOS update or two. Usually it recognizes the issue quickly and delivers a patch. On Nov. 10, an Apple Support Forum rep responded to users' concerns by pointing them to articles on Maximizing Battery Life and Lifespan. One user complained the answer was "nonsense." Mashable has contacted Apple for comment and will update this post with its response.