I didn’t see anything while searching but this basically happens to me since update 31 (never before) Alliance mates don’t have same issue.
I type something into alliance chat but DON’T hit done.
Leave game, usually for only a few seconds like to look up a hero card, attack stack etc.
I return to game and my message has posted in alliance chat despite NEVER hitting done. Tested about a dozen times.
I understand this is relatively small thing, but still odd. I’m on iPhone 10, phone and game both updated.