Andriod phone disconnected randomly from Wi-Fi

[Gaurav1]

We like to use Andriod phones as SIP clients but Phones disconnect from network randomly. They may not disconnect for 2 days or may disconnect in 2 hours. If two phones sitting next to each other, one stays connected, another disconnects. To bring them back, we need to move out of coverage area and come back or turn off the wi-fi and turn on again. We have cisco WLC and cisco APs for wifi network.
I used an APP called Wi-FI fixer, and attached are logs

[Gaurav1]

I am using zopier or Csipsimple app from Android store but it is network disconnection issue.

I could understand if network drops after 30 mins but it is very random. sometimes it works for 2 days.

[RobertZ]

can you provide more info on the sip client?

[Gaurav1]

Thanks, I am using a Samsung S5 phone. Can't see much information from WLC.

it is very random.

[Timo1]

Sounds like a client problem. What devices do you use? Any logs from the WLC?