The iPhone 4 “grip of death” signal-strength problem stems from a bug that has been with Apple’s bestselling smart phone all the way back to the original iPhone, Apple announced Friday, saying it had found a “simple and surprising” cause for the widely reported reception issues.

But Apple’s “explanation” raised more questions than it answered.

“Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong,” the company wrote in a statement posted on its website. “Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength.”