Observers are inconsistent on chunk borders

Bug

Observers are inconsistent on chunk borders.

How to reproduce

1. Place a line of observers facing towards/crossing a chunk border

2. Update all of the observers at the same time

What I expect to happen

All the observers will output at the same time

What actually happened 

Some observers will update before others, causing an inconsistency

 

This bug affects multiple Redstone contraptions, especially things like piston doors, flying machines, or anything that uses observers.