Can you help me understand these two issues I'm facing?

https://reddit.com/link/1jdfx75/video/yde525vht9pe1/player

I'm making a 2048 clone. The "GameBoard" scene has a base that is a panel container.

PROBLEM 1: When adding the GameBoard scene to the "Game" screen scene, as a child of the base control node, it retains it's background, but when added as a child of the VBoxContainer child (or even of a margin container that was a child of the VBoxContainer, as I was previously doing), the background color of the GameBoard panel container is lost. This was also the case when the base was just a panel rather than a panel container.

PROBLEM 2: The neither the VBoxContainer nor the MarginContainer I was previously using as a parent of the GameBoard expands with the size of the gameboard... Any idea why?