In vim: stop SHIFT+SPACE from discarding all unsaved changes

Every time I type Shift+Space in vim, it undoes all changes to the file that have not yet been written. I would like this to not happen, as it is extremely easy to press Shift+Space by accident. I am using iTerm2, and am ssh'ed into a remote machine. When I use vim (in iTerm2) on my local (OSX) machine, this issue does not occur. When I use the default terminal instead of iTerm2, this does not occur, even when ssh'ed into the same system. So: only the combination of iTerm2 + being in an ssh session seems to cause problems. I have never modified any vim keybindings; I have no ~/.vimrc, and :verbose Map doesn't show any binding. This makes me think this is an iTerm2 issue - but I don't understand why it would not cause this problem when running a shell on my local machine. Are there any iTerm2 profile settings that apply only in ssh? Or should I look elsewhere for this issue?