If the title contains the ‘&’ character, the rendering engine throws an error.
It appears to happen only with custom shapes.
Here is the screen-shot from the DHX demo page
This is the expected behavior. As you are using the html in your shape template you need to escape all the special chars in it.
Hello shoiiin
We have afixed your reported proibl;em in the latest (3.1.0) dhx.Diagram update.
Now the special chars should display correctly in the custom templates.
Thank you for your report.