When on layer 2, Mario has a higher Y speed than normal which helps him move smoothly on layer 2 vertically. However, this also make him drop much faster when walking off of layer 2 ground rather than jumping off. This patch fixes that.
This reminds me some sprites, more specifically mushroom sprites affected by gravity to instantly fall down ledges (not a layer 2 issues, happens on ANY ledges on ANY layer). I believed it's due to its Y speed in its code forgetting to zero out ($AA,x) when $1588,x's bit 2 (down bit) is set