Reproducing the bug:
1. Settings -> Preferences
2. Go to tab "Language Menu/Tab Settings"
3. Turn on "Replace by space"
4. Create new document.
5. Write "html:5" and expand, it still gives the content in hard coded one tab indentation.
1. When expanding snippet look for tab characters in beginning of lines.
2. Replace these tabs with appropriate global settings.
(This requires that all presaved snippets use Tab character as indentation)