I would advise downloading a fresh version of the theme from your themeforest account and reinstalling via ftp to replace the existing version.
Make sure you don’t have WP Debug on, it needs to be set to false otherwise you’ll see all kinds of warning notices – https://codex.wordpress.org/WP_DEBUG
If debug is off and you still have problems, make sure you deactivate all third party plugins in case they’re causing a conflict. Then make sure you’re on WordPress 4.1.1. Before reactivating any plugins check to see that the issue has resolved. Then reactivate your plugins, and if the issue occurs again, then you’ll have to go through your plugins one by one to find the one causing the problem.