skeleton spawner turns empty( not found empty, turned empty)

Ok so i found a skeleton spawner in my world (SP) and it used to work but not anymore. (mega edit) (ok so more information? hmmm.... Skeleton spawner found, skeleton spawner worked, skeleton spawner dosent work anymore, it looks empty, still have the flame animation inside the box,no skeleton animation( 306' skeleton spinning sutff) if you look at the video i linked you can see me in range of it so it should spawn stuff, difficulty is on hard light level is 0 i checked the basics, forgot to link F3 screen my bad. did a chunk refresh( its inside the spawn chunks) tried to duplicate saves files and play around in the level.dat stuff and didint work (made a backup) havent been in range for quite a while like 2 or 3 days(real life days) (as in range of the spawner)
this is all i can think of on information honnestly