Apple said it plans to release iOS 8.0.2 in the coming days after it was forced to withdraw the latest operating system update over complaints that it caused calls to drop out on the new iPhone 6 and iPhone 6 Plus.
Apple said on its website it was working on a fix for the issue.
"We apologise for the great inconvenience experienced by users," Apple spokeswoman Trudy Muller said in an email.
Users of the iPhone 6 and 6 Plus complained about a drop in cellular service and inability to use the fingerprint-reading Touch ID after updating to iOS 8.0.1.
Other users had complained of "sluggish wi-fi and dwindling battery life" after moving to iOS 8, Time magazine reported earlier this week.
The new phones also face criticism over their bendability, dubbed "bendgate". Social media and online forums have been abuzz with comments about how the new phones can bend when placed in back pockets or while wearing skinny jeans.
"I do believe this speaks to execution issues at Apple," said JMP Securities analyst Alex Gauna.
"At the end of the day I believe this too shall pass, but we are noting with concern that the miscues pile up."
Apple shares slid nearly four percent to US$97.72 (A$111.27) in early trading, to be the biggest drag on the Nasdaq Composite Index. At that price, the stock had lost all its gains since the launch of the latest iPhones and the company's market value declined by US$24 billion (A$27.33 billion).
On Thursday, Apple issued a step-by-step guide for users to reinstall iOS 8, launched last week, through the latest version of iTunes. The health app Healthkit will not work for now and will be fixed in iOS 8.0.2, the company said.
Rival smartphone makers took digs at Apple's problems.
A Samsung advertisement showcased a bending phone against its own product, while BlackBerry CEO John Chen said "I would challenge you guys to bend our Passport."
Update: Apple has released iOS 8.0.2. Click through for more.