Update 2/5/20: Infinity Ward have updated their Trello board to acknowledge the issue and that they are working on a fix:
Warzone ushered in a new age of cross-play and now we have a new issue to worry about besides the hacking. Since there’s no party chat option across platforms, squads are forced to use game chat. Unfortunately, game chat has been broken in the latest Warzone update, occasionally going off randomly during a game and even muting your teammates without being able to unmute them.
Since comms are so crucial in Warzone, this can be considered a game-breaking bug and forced me and my squad to stop playing last night due to the frustration of the issue.
If you too are experiencing this, you are not alone. A thread on Reddit has gained support to try and get an answer from Activision Support who are seemingly yet to even acknowledge or respond to the issue.
Once Activision or Infinity Ward address this issue, we’ll update this article so you know when to expect a fix.