XMPP chat application "both" subscription issue cross plateform

We are creating an application which runs on cross platform(iOS & Android). It runs on timer based.
A user will send chat request to B user and once B will accept,we are starting timer simultaneous on both devices on receiving "both" subscription from jabber. The Problem is  sometimes we are not receiving both subscription on both end and our app stops working. Is there any work around to deal with such kind of requirement? I have posted questions on other community as well. Code we are using for request/accept on both end is mentioned in Cross platform (iOS-Android) xmpp request - Stack Overflow  query. Please help me in this issue. I have attached the code sequences we are getting on successful scenario.