The location of the initial player spawn can change significantly when 'Caves and Cliffs' experimental gameplay is toggled on. No matter where the spawn is without the toggle, with it the spawn was always near on a gridpoint near 0,0 (most seemed to be -32, Y, 0 or -32, Y, -32 but there were a couple like 64, Y, 0)
Stronghold below in the seed picker is affected by this bug.