Often SublimeText 2 opens files and if it finds in some place some spaces instead of a tab.
I said to force everything to 4 tabs. Not to convert manually every file I open to tabs (like in How to replace four spaces with a tab in Sublime Text 2?)
Sometimes I have a document with tab indentation of 4 spaces and when I press tab it writes 4 spaces!
"detect_indentation": false,
"translate_tabs_to_spaces": false
(doing tab_completion=true it helps)