Strongholds sometimes don't generate the End Portal

Haven't been able to locate the end portal in strongholds in version 1.0.0 on windows 10 or Android I used eye of ender twice to find stronghold (Because the locate command produces an error..!) but despite excavating the entire structure found no end portal.

Examples:
Seed: 8
Coordinates: -1402 -47 -1500

Seed: 34031138
Coordinates: 932 31 1807