The bug

jackolanterns and redstonelamps have become non spawnable blocks, meaning for example slimes will no longer spawn on them. this has been used alot in farms and other contraptions since these are the only 2 full cubes that provide light while still beeing spawnable.

This was most likely introduced with the changes to glass that made sealanterns etc spawnable, wich was afterwards fixed. jackolanterns and redstonelamps shouldnt have been changed