Bed blocks have a white texture on the inside, which probably shouldn't be there - there's absolutely no need to waste resources on rendering a face not normally visible under normal gameplay circumstances.

To see this face in survival:

1. Create the following setup (dirt can be any solid cube, glass must be glass, and snow must be eight snow layers)

2. Walk into the glass block/bed, and once pressed up against it throw an ender pearl or two at the ground while holding the forward key

3. Note a large white rectangle:

This could be fixed by converting beds back into using block models, rather than entity models. Through block models, this white face could be completely omitted from the json file, like how the top/bottom faces of the bottom/top halves of doors are. This would fix other issues that arise from beds using entity rendering, such as them disappearing at far distances when still within rendering distance, allow them to be remodelled like almost all other blocks through json files, allow other faces such as the bottom of the legs to be culled where neccessary, reducing lag, among other things.