If you are using Join/part for detection of who is in a channel see this URL/API/endpoint instead:
http://tmi.twitch.tv/group/user/cohhcarnage/chatters
Swap cohhcarnage accordingly for your channel. And FYI this is a unofficial/undocumented API.
Join/part/membership tags is best for +O/mod detections or the proper IRCv3 TAGs and the user-type tag