Why does this train station unload unequally

[smurphy1]

I created this train station to unload ore from my mines.

station.png (1.24 MiB) Viewed 6373 times

My understanding of belts and splitters says that if the chests are all full, all the belts between the chests and the balancer are full, and each train car has the same load then all the cars should empty at the same time. This is true at first however after several in-game hours the train cars will be uneven with the cars at the right end being empty and cars at the left end being nearly full while the cars in the middle being almost empty. What's even more bizarre is that I have several similar stations throughout my base and they all exhibit this problem over time. All these stations the trains enter from right to left and it is always the right cars that empty first and the left cars that empty last with the gap growing larger over time. This is despite the fact that they are routed through a balancer and that while the consumption of the output belts is not even it is still different from station to station (for example in one station the top output of the balancer is consumed the most downstream while in another station the top belt isn't used at all yet both unload unevenly in the same way).

What am I missing? Is this a bug?

Edit: Here is another station that is showing the uneven unloading.

station2.png (1.43 MiB) Viewed 6371 times

[DaveMcW]

Splitter-based balancers only work properly under constant load. When lanes back up they start to become unbalanced.

[smurphy1]

Splitter-based balancers only work properly under constant load. When lanes back up they start to become unbalanced.

If belts are going to back up at some point what options are available to mitigate or fix this?

[DaveMcW]

You can use inserter based balancers. http://reddit.com/4e03g2

[impetus maximus]

here is how you can ensure your chests are unloaded evenly.

even.unload.png (430.12 KiB) Viewed 6257 times

wire all 48 chests together with a red wire (for example). connect them to the input of a arithmetic combinator set to 'ore / by -48 (negative number of chests) output ore.
string red wires from the combinator output, to all the inserters UNLOADING the chests. then take a single green wire for each inserter and connect it to only the chest it's unloading.
next set the inserter to enable if ore is > (greater than) -12 (for fully upgraded stack inserter bonuses.)

this will average out all the chests to make unloading even. if the chests are in an unbalanced state it may look broken (many chests not unloading)
just give it time and the chests will even out. the reason for the negative number used on the inserter. if we used > 0 for example, if the chests were all average ALL the inserters would stop.

[Optera]

For chest to belt you can also wire all inserters together, set them to enabled if everything = 0 and read hand hold.

2017-03-23-07-12-08-9703356.jpg (102.34 KiB) Viewed 6247 times

Now the inserters of one belt segment will wait until every single one has placed their items on the belt.
If you use belt segments spanning 12 inserters ofc wire all 12 together.

[DOSorDIE]

For chest to belt you can also wire all inserters together, set them to enabled if everything = 0 and read hand hold.

2017-03-23-07-12-08-9703356.jpg

Now the inserters of one belt segment will wait until every single one has placed their items on the belt.
If you use belt segments spanning 12 inserters ofc wire all 12 together.

Genius!
That i missed in my Train Unloading system
Thanks!