I play on a cross platform dedicated server. Through out the day. There will be times both natural spawners and added in spawners will quit working. On one instant a player was using a natural spawner and mine quite working then I went to another and his quit working. I have a added one near my base when I pass it and go to a natural skeleton spawner in a mine the skeleton won't work but I go back and added in one is. It seems to happen alot 1 hour before reset. Seems to be a problem when only acouple of players are on say 2 or 3. They they stop working I check the location of all the spawners I know of and they are not working either. All areas are cleared of blocks by 9x3x9 space. No light sources near by total darkness. It won't let me add video or I would show it.