CC2540 connection interval update fail

I comply Apple rule about connection interval update, such as timeout=6s, min=0.5s, max=1s, latency=0.

But every time i update connection interval parameters. iPhone5 will disconnect with CC2540. iPhone4s is better than iPhone5, but iphone4s will lose connection.

So i think if my 32.768K is bad?

I measured 32.768K crystal, and Peak-Peak is 300mV,  i change capacity from 6.8pf-20pf.

But same problem happened.

I measured 32MHZ crystal, and Peak-Peak is 500mV.

So any other people have this problem.