Indefinite hang when trying to attach to tmux -CC

Bug report

Thanks for filing an issue! Please answer the questions below so I can help you.

• iTerm2 version: 3.5.3
• OS version: 14.6
• Attach here (drag-drop from finder into this window) com.googlecode.iterm2.plist
• Attach a debug log, if possible. debuglog.txt
• Attach a screen capture video if it would make the reproduction steps clearer.

PLEASE ATTACH YOUR PLIST FILE FOR BUG REPORTS! Seriously! I'll probably ask you for it if you don’t.

Detailed steps to reproduce the problem

1. ssh via aws ssm to remote machine
2. tmux -CC attach -t <session_name>

What happened

I see ** tmux mode started ** but the new tmux window never opens

What should have happened

I should have had a new iTerm window open with my tmux session

When this problem occurs, I just quit iTerm, re-open and try again and again. Eventually I am able to connect and the new window opens upon one of my retries.

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