Power/Lock button not clicking, difficult to press
Yesterday the power/lock button on my iPhone 4 stopped having that satisfying click when I pressed it. At first I thought it was just that my phone is getting old and losing the nice tactile feel, but now it's getting harder and harder to get a response out of the button.
It does still work if I press it hard enough and in just the right spot, but it seems to be getting worse as time goes on. Right now I have accessibility settings enabled so I can sleep my phone without the button.
I've read some guides on here and I'm not sure exactly what part I need (or if I need a part at all). I don't believe it's the button itself that needs to be replaced (if anything it's probably the inner mechanism), but it seems a few people have been successful in fixing this problem without replacing anything.
I don't want to take it in and pay obscene amounts of money to have it fixed and I know a few people who are good with electronics so I'd just like to order the part, but I'm not comfortable taking the phone apart myself.
this is a problem of power button black dot on it . Dismantle the iphone completely.
after removing all the things . you will see the power switch has a yellow sheet on the power button and black dot on it. if small black dot is not there then find the black dot and placed on power switch. otherwise change the power button flex.
I am not sure is there any way to solve this problem but i am sharing one of my friends experience after he got such kind of problems.He goes to apple store and let the Mac Genius know about his problem and he said it is a hardware defect and went ahead with the swapping process. They had some replacements in the back.It looks like the genius nicked the chrome bezel with the charger cable edge, and there is a bit of a light leak.
Here is a video of this problem solution you can check it too -