I'll leave this post here if anyone runs across the same issue. Under Alpha in the layer texture node right click "Layer is visible" set key, move to the next keyframe, uncheck the box and set a...

Maya Ver: 2020.2

Setup: Layered Shader (also tried a Layered Texture hooked up to a blinn color), two layer nodes that have textures, Compositing Flag is Layer Texture, select Frame 1 on timeline,...