iPhone locking sound delays

[MNFL]

hey guys
so when I lock my phone, the locking sound delays for 3-4 seconds. this have started to happen recently. anyone knows what might be causing this?

thanks
MNFL

 

[iphone4champ]

What iPhone is it? Also could be a memory issue.

 

[MNFL]

What iPhone is it? Also could be a memory issue.

iPhone 4S. I tried freeing up the memory, but same result

 

[Surminga]

I had this issue on my last one, 3gs towards the end of its life, I just restored it and refreshed it