Hi,
and thank you for writing in!
We’ve just tried it in our local installation and it works fine!
Please, try to deactivate all plugins, leaving only WooCommerce and YITH WooCommerce Product Bundles active, and see if the problem is solved. If so, try to activate them again, one by one, to see which one causes the issue.
If the problem isn’t caused by a plugin, try to activate the default theme Twenty Sixteen and see if you have the same issue.
Also, if you have customized some files in your theme, please try with a fresh installation without any customization.
Please try this solution and let us know what’s the result.