Apple Inc. before the release of iPhone 6S and 6S Plus also introduced the iOS 9 for all the smartphones that are running on the iOS 8.1. The early adopters soon started to encounter bugs that were disrupting the usage. Also, a new feature known as Wi-Fi assist was spiking the cellular data consumption on the smartphone.
This newly added feature from the Apple let the users enjoy seamless Internet even when the Wi-Fi isn’t working properly. As soon as slow internet is encountered on the Wi-Fi connection, the iOS switches the connection to the cellular data without any warning. Users thought that they are on the Wi-Fi where they were consuming the data from their limited cellular plan.
However, there is a way by which you can turn that off. Settings > Cellular > scroll to the bottom and disable Wi-Fi assist. After doing this, you will not be able to encounter any data spikes.
Apart from this, in the initial releases of the iOS 9, users had a lot of trouble with the newly launched iPhone 6S and 6S Plus. Firstly, the smartphones were getting switched off randomly, and the TouchID was too hot to touch. iPhone started giving the high-temperature warning sign and turned off instantly to save the internal components. However, they were only being used at the room temperature and weren’t exposed to the heat. The problem was of the iOS 9 as there were no such issues after the reset.
Other than this, many users reported about the faulty display with dead pixels in the corners. Not sure what was the reason behind it, but as soon as you boot the smartphone dead pixels start to appear in the corners and go away soon the smartphone is restarted.
So these were the issues that were reported by the Apple users on the community forums, and Apple should fix them as quickly as possible with a stable release of the iOS 9.