terminal: vi editor strange behavior

Hi,

I noticed something strange recently in Terminal app.

When editing a file with the editor "vi":

- press i to insert text

- press ESC to switch to "escape mode" : this doesn't work anymore. You need to press CTRL+C

The same problem exists with Terminal app or the third party iTerm.

Also, it's the same whether the file is edited locally or on a remote machine using ssh (i.e. Linux)

Has anyone noticed the same issue ?

Thanks.