You can try and figure it out using the developer tools included with each of the leading browsers (look in the browser menu(s) for developer tools, error console, etc.).
If you can't figure it out, you're welcome to attach a Tersus project demonstrating the problem (use File>Export...>Tersus>Tersus Export File to create a .tersus file from your project). Also include instructions on how to recreate the problem, and details of your environment, especially your Browser (and version).
For best results, use the Firefox browser..