I downloaded the Bootstrap 3 theme yesterday and applied it to my site but for some reason the theme appears to be very buggy on Vanilla 2.1.1... Has anyone had this issue and know of a fix?
it may sound like a good description to you, but it really doesn't impart any information.
fix what, no one knows what needs to be fixed until you display a screenshot, or the issue.
I may not provide the completed solution you might desire, but I do try to provide honest suggestions to help you solve your issue.
if your question refers to a theme in the add-ons section - best to ask question there, or on github if the author requests issues to be posted on github, if you want response from author.
I'm using Bootstrap on one of my forums (http://kraftgame.tk, vanilla 2.1.1), And it works perfectly.