Hi there! From what you describe you seem to be running into GPU memory limits.
As you probably know everything in Lightning is a texture, and those textures are uploaded to the GPU. When the GPU runs out of memory to upload new textures and not enough textures are being released, the GPU typically will render black blocks, where you’d normally expect an image or text. And it can display flickering during animation, simply because there’s not enough memory left to animate smoothly.
On your computer the memory of the GPU is pretty much unlimited, compared to that of a STB. That’s why you’re only seeing it there.
You might be interested in going through this long read on Memory leaks in Lightning - specifically the part about GPU memory leaks. The article explains in detail what memory leaks are, and how you can prevent and tackle them.