I hope someone can help me with this. I've found that there is a border gap between the perimeter of the slide and the player in Articulate 360, when the player is scaled to fill the browser window. I've attached a png to show what I mean.
In Storyline 2, there was no seam between the slide and the player when I chose to create custom CC on the slide. In Storyline 360, there is a persistent gap between the CC rectangle on the slide and the player.