Apple's hopes of enhancing performance and speed after upgrading to iOS 9 seem to be crashing. Several users have reported various problems, ranging from sluggishness and sudden crashes, to unresponsive "slide to upgrade" screen, after updating to the new software.

Apple is taking one issue at a time and has released a new support document to fix the unresponsive "slide to upgrade" that refuses to go away.

The official support document by Apple gives three simple steps to fix the unresponsive screen issue: 

Step 1: Connect your iDevice to a PC and launch iTunes. (Use the same PC where your data is synced on iTunes)

Step 2: Select your device on iTunes.

Note: If iTunes fails to recognise your device, force a restart on the device by holding down Sleep/Wake and Home button for at least 10 seconds. You can release the buttons when you see an Apple logo.

Step 3: Restore your device from the backup you created before upgrading to iOS 9. In case you did not back up your data, take a backup first and then perform a restore.

While Apple has addressed the issue at large, there have been complaints about the same problem on Apple Support Communities.

"I updated my 4s to iOS 9 today. After the update finished, my phone restarted and asked me to connect to wifi. then it went to a white screen that says "slide to upgrade" but it is unresponsive. I tried backing up my phone so I could restore it, but iTunes just says "Backing up Iphone" but it doesn't seem to be working. I let it sit for hours but nothing happened. I then tried to restore it and it says i can't because "find my iphone" needs to be turned off. I can't access my settings on my phone because it is stuck on that screen," a user said on Apple Support forums.

Other than this, iOS 9 device users have also reported problems like sluggish performance and sudden crashes. Apple is yet to officially release a fix for the problem. Clearly, the next update, iOS 9.1, is expected to come with all major bug fixes but the release date has not been fixed yet. 

According to Reuters, Apple is reportedly aware of the crashing issue and the engineers are working on a fix.

"They said they were aware of the problem and their engineers were working on it 24/7, but they couldn't tell me when - or how - I would get a solution," an iPhone user Zorry Coates said.