Snapshot 459, users are unable to sleep in a bed (says it is occupied) and when using a sleeping bag they fall through the world and die.

Sorry, I'm unable to reproduce any on issues (even on non-dev server with two players). Please check (when possible):

• if issue is still present without OpenBlocks
• if there are any interesting entries in logs when players sleep
• if players fall through world while sleeping or after waking up

Is this related to the max sleep height Y128?

I just tried sleeping above this height (where a normal bed just throws you back out of it) and the sleeping bag sent me straight into the void.

This issue is probably no longer valid, since I changed that code few times already.

I can't reproduce your issue in recent version.

That issue was using OpenBlocks-1.7.10-1.3-snapshot-549 sorry if it's old

No, this snapshot is not old. But your problem is probably separate issue. Anyway, I can't reproduce, so it's probably interaction with other mod (or spigot if used)