Hello Minecrafter,

as you can see in my screenshots, multible stacks (16-20) put recently in a chest will vanish sometimes.

The environment:
I had the couple of chests, most of them empty. Just the two rows with the torches are all full of stones. About 10 double chests at the right are full, too. The rest is emty.
Not fare away you can see a 1x1 stone tower. At his base I placed some full double chests with unsorted stuff, mostly dirt, grass and stone.
Render distance was 4 chunks.
About 80-140 blocks away (north) from the chests are my animal farms with about 600 Animals of all kinds but there wasn't big lags with the 4-chunks render distance.
It was peaceful.
I run in on 1.8.8 (latest) but this place was generated some releases bevore.
The 4 beacons gives Haste II, Speed II, Resistance II, Strength I and Regneneration I.

My proceeding:
I crushed 0.5-3 full double chests, ride there with my horse to fill my inventory instantly, then ride back and sort it in the chests. This took me about 40-70s for 1 ride.

My problem:
As you can see in the two chest-screenshots, I sort my stuff in the chests and it vanished.
First picture: I am about to fill all my 16 stone stacks in the double chest, then go for the dirt chest and repeat it.
Second picture: It's 44s later, same chest, and the chest is still as emty as bevore. The 16 stone stacks I put in 44-approx.39 s before are gone.

I am sure:
You can easily get crazy with that mass of chests and all the different inventorys, but I am sure.
I made a film of my screen and, believe it, there's the same bug.
I put 25 dirt/grass stacks in a 23+2-stacks full double chest and they are gone after 55s, when I wantet to sort in some further stacks.

Often but insecure in reproduction:
This happends, while clearing about 40 full double chests, quite often, but not always. The items wont vanish every time. I got about 20-25 double chests full, at least. I am not that sure, but with the gravel and coal/... resorces (just 1-8 stacks/ride) this bug didn't occure. I had the feeling, this bug won't occures twice in a row (maby not true) and, more secure but not proofed, won't occure if you fill a chest entirely. Maby it doesn't occure, if you take longer then 1 min with your ride. I drive mad after some hours of Minecraft, but I had this feeling, too.
I put many stacks in many chests in my 1768-day-world, but this bug is new.
I didn't back up the world recently, so I can't reproduce it easily.

I never expected that devastating kind of bug in your woundeful programme.

Kind regards,
fTester

.
Ps: this was private, because I dont like to publish anything.
We can discuss about that, though. (right word?)
Pss: If you really want, I may could send you my video, too. (But my face mirrors in the screen and I don't like to publish that (not that my face is bad))