Spawn Chunk or summon item age no longer functioning

At spawn amongst many command blocks we have this commnd running to continually enable triggers for players: /summon Item -4 12 5 {Item:

{id:clock,Count:1}

, Age:5990}

When anybody is in Overworld, this works as intended and everything works fine, however upon testing in the b vers of the snapshot, when no user is in overworld, instead of remaining to keep working, it stops and all commands//triggers running from that clock stop functionning untill a user returns to overworld.

During the period after killing the Enderdragon till XP has all dropped things start working momentarily, but end up stopping again.