As there is a delay in updating Hearthstone on iOS devices^^ and that different Hearthstone versions can be online at the same time and considering that users cannot play matches against friends with different Hearthstone versions, but are still able to chat with friends using different Hearthstone versions,
What happens if: a user (A) having the old Hearthstone version logins and CHAT with a friend (user B) having the latest Hearthstone version, then user A tries to challenge user B (but cannot) and realize that its Hearthstone version is not up-to-date and prevent it from challenging a friend, user A would then logout and update Hearthstone then log back in and maybe notice that the new update has a bug preventing it from chatting?
What has actually changed in Hearthstone functionality between those two updates (around Oct 16)?
Could it be that the header file of the chat history (to download/retrieve when opening the chat box) has been updated? If yes, then that outdated header file may be present in the chat history of user A, as he would of chatted with an outdated Hearthstone version on a possible new version of chat system, which could maybe results after updating Hearthstone in having its chat services being unable to retrieve/read properly the outdated header file of chat history so opening the chat box would result in the game crashing (simply by having chat from an outdated Hearthstone version)?
I hope this helps