How to make DrupalChat more stable, to have it recognise online users?
In the module config page admin/config/drupalchat/configuration see Chat List Latency says


  The delay, in seconds, after which the user will be shown offline in
  the chat list(i.e. removed from the chat list) from the time he/she
  goes offline. Increase this value if you find the chat list is
  unstable and keeps on changing a lot (for example - when a user
  navigates from one page to another he/she goes offline and then comes
  back online again). Decrease it if you find that the users are shown
  in the chat list for too long after they have left your website.