Spawners do not spawn entities at the correct position anymore or do not spawn them at all, which might be caused by the fix of
Spawners spawn any entity that has NBT tags other than id but no Pos tag at (0|0|z). This means only their z-coordinate is used.
Monsters with no other NBT tags than id an no Pos tag are spawned at (0|y|z). This means only their y- and z-coordinate is used.
Use the following command