I've tried the latest version of tmux in debian, but this suffers from the same problem when running as "tmux -2" and setting TERM=xterm via 'set-option -g default-terminal "xterm"'.
I've also now seen the problem with a plain urxvt terminal *and* a plain xterm (both with TERM=xterm) suggesting the problem is with the terminfo database.
I've tried the latest version of tmux in debian, but this suffers from the same problem when running as "tmux -2" and setting TERM=xterm via 'set-option -g default-terminal "xterm"'.
I've also now seen the problem with a plain urxvt terminal *and* a plain xterm (both with TERM=xterm) suggesting the problem is with the terminfo database.