Most VIM folks remap for quicker window pane navigation. So instead of hitting Ctrl-wh to move the cursor to left window pane the Ctrl-h key is remapped to do the same thing.
Ctrl-H is “ASCII backspace” but terminals ought to be sending ASCII DEL for the Backspace key instead. Which means to go to the left pane I had to type C-w-h. Found the above solution in this lengthy thread for NeoVIM Issue #2048 and it should work for VIM users as well.
This has been driving me nuts this week since I’m back on OS/X from Linux. Decided to hunt down a fix tonight and found a very simple solution.
For future reference, this is how to configure iTerm2 to send the correct CSI for
Edit -> Preferences -> Keys
Ctrl+h as Keyboard Shortcut
Send Escape Sequence as Action
[104;5u for Esc+