Comment by qudat

> Setting TERM properly isn't some tmux-specific problem.

Correct, but it's another layer to deal with. There are `tmux` specific TERMs that should be used which sit on top of your terminal emulator TERM. This was my point: you have another layer that you need to be aware of when using tmux and when debugging.

Just look at the top of tmux's FAQ:

https://github.com/tmux/tmux/wiki/FAQ

> PLEASE NOTE: most display problems are due to incorrect TERM! Before reporting problems make SURE that TERM settings are correct inside and outside tmux.

> Inside tmux TERM must be "screen", "tmux" or similar (such as "tmux-256color"). Don't bother reporting problems where it isn't!

> Outside, it should match your terminal: particularly, use "rxvt" for rxvt and derivatives.