Time to add another complaint about the iPhone 4 to the list? Over at Apple's support forums there are a significant number of complaints about the smartphone's proximity sensor, which is generally used to shut off the iPhone 4's display whenever you're holding it against your face. According to various owners, the sensor isn't consistently recognizing proximity and thus randomly activating the touchscreen mid-call; that's leading to calls being accidentally muted or ended, or second calls initiated.
Some are finding that the proximity sensor works if completely covered with a finger, but not when used normally; that could suggest that the settings are at fault rather than the hardware itself. If so, Apple might be able to address the dicky sensor with a firmware tweak, rather than having to physically change units.
This new issue joins complaints over poor reception, which Apple has acknowledged is due to the external antenna design for the new iPhone 4. The company maintains that either modifying the way you hold the smartphone, or using a case such as its own Bumper, addresses the problem; however at least one law firm is considering putting together a class action suit to represent disappointed owners.