Spotlightr is a fully responsive player and that means that it adapts to the size of the element/container in which you place it on your page.
This means that if the element in which you place Spotlightr is hidden by default, for example, in a collapsed accordion or inactive tab, or any similar occurrence, then Spotlightr will adapt to the size of the element as is on page load.
Spotlightr can't listen for activity on your page since that would violate many security and privacy principles so you need to let it know when an event has occurred which unveils or shows the video.
We've addressed by adding an option in App Settings >> Global Options. You can enable the option Force Resize When Visible:
If you experience difficulties with the proper sizing of Spotlightr, our support team is here to help.