We experienced problems on a site where we inject our widget and dynamically load Handlebars runtime when the host site already has loaded handlebars.

In the initializiation the Handlebars object is freshly created nevertheless if there's already an object or not. That leads to overwriting already defined templates.

A simple workaround is to add code similar to that:

var Handlebars = Handlebars || (function() { /* code */ })();