Apple's stock was down around 3.5 percent on Thursday, after some customers complained that a software update interfered with voice calls on their new iPhones, while others noted that the larger iPhone model could be vulnerable to bending.
The stock decline led a broader decline in technology shares.
While the bending problem may not be widespread, Apple was forced to withdraw the software update because of glitches that appeared to primarily affect customers who had purchased the new iPhone 6 and 6 Plus models. Late Wednesday, the company offered users a way to manually reverse the update provided earlier in the day.
Apple said affected users can connect their phone to a Mac or Windows computer and download a file to restore an earlier version of the iOS 8 software. Apple offered a Web page with instructions: http://support.apple.com/kb/HT6487 .
The company had begun distributing the update Wednesday morning to fix several issues in last week's iOS 8 operating system for iPhones and iPads. Hours later, it pulled the update, dubbed iOS 8.0.1, after some people complained it rendered their phones unable to make calls and caused problems with a feature that lets people unlock their phones with their fingerprint.
Users are still able to the upgrade older phones to last week's version of iOS 8, which Apple said has already been downloaded to nearly half of all iOS devices. Apple said it will release iOS 8.0.2 soon to address both last week's glitches and the new ones.
It's not uncommon for new software to contain bugs that have to be fixed with subsequent releases. Apple has also grappled with other problems affecting new iPhones in the past — most notably, the complaints about poor reception and dropped calls that affected new iPhone 4 models when they were released in 2010.
Meanwhile, social media sites were buzzing Wednesday with reports that the aluminum shell of the iPhone 6 Plus is vulnerable to bending. Some Twitter users claimed their phones showed a slight curving at one end after several hours in a pants pocket. With a 5.5-inch screen, the iPhone 6 Plus is slightly longer and thinner than other iPhone models.
It's not clear how widespread the complaints are. One YouTube video showed someone bending an iPhone 6 Plus by applying extended pressure with his hands — not from normal sitting.
Both the iPhone 6 and the 6 Plus were given high ratings in a recent "breakability" test conducted by SquareTrade, a San Francisco firm that sells extended-protection plans for electronic devices. The test did not include bending.
SquareTrade Chief Marketing Officer Ty Shay said that after reports of bending circulated online, two staffers at his firm tried to bend a pair of 6 Plus phones. The male staffer was able to duplicate the results from the video, while the female staffer could not. He said the bent phone appeared to still function normally.
Shay said his firm then checked and found a small number of bent older-model iPhones had been reported in the past. "It does happen," said Shay, "but it seems like for the most part it's cosmetic damage."
He suggested the bending is not a major issue. Referring to the iPhone 6 Plus, he added, "I think it's still a very durable phone. But we'll keep an eye on the claims."
Apple did not comment on the reports of bending.