From some time (can't figure out from what change) I noticed that "Sublime Text 3" started duplicating classes and input in auto-mode with no reason at all. Sometimes it starts to write something on the beginning of document etc. It may be because of packages\extensions, I still can't figure out.
I put all files on GitHub, will try to look for a reason of this bug. Was searching for it, but didn't find anything. Keyboard works fine, the touchpad was switched off.
Looks like the "Emmet LiveStyle" extension duplicates text and have some bugs with input\output. There was no fixes for LiveStyle extension still and only way is to turn it off - if it works too buggy. I turned it off and everything works for me perfectly. There was the question with the same problem, but it has another title - Identify duplicate styles css - people just turned off the LiveStyle extension.
The best alternatives for "Emmet LiveStyle" are "Emmet" and "LiveReload" (https://github.com/alepez/LiveReload-sublimetext3 LiveReload)+browser extension/free guard-livereload OS extention http://livereload.com/; LivePage - additional chrome extension.