Content of chest disappear when passing fro 1.7.10 to 14w31a

Did you play the world in 1.7.10 or earlier after playing it in the snapshots?

I first played it in snashot. I played it in 1.7.10 to resolve the problem that nothing was spawning in te nether generated before a napshot. It works, but my chests are now empty.

Downgrading is not supported and WILL cause issues like these. I hope you made a backup of your world.