can't find the biter spawner

[tinyzzz]

i create the map in ver 1.1.109-0 and play hundred hours with no enemy and peaceful and not playing with any mod.
after covered the map into spaceage i can't find the biter base.

but i create a new map in 2.0.23 with no enemy and peaceful , i do find the biter base

the map code:
>>>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<<<