Based on the provided information it would be hard to pinpoint what is causing the behavior. Nevertheless, would you disable any custom styles that are applied on the page and see if the behavior changes.
Also, make sure that you are using the latest version of the components. The current release is 2017.2.504.
In case the behavior persists please send us a runnable sample or a dojo demo
where the behavior is replicated. This will enable us to examine the issue locally and look for its cause.