What's wrong with my chests (Minecraft)?

Since today my chests are now and then put out individually, although I didn't like it that way.

It happened to me for the third time today.

Why is that so?

Thanks in advance!

This happens when you sneak while placing the boxes

A little tip in case you don't know:

You can place item frames where the signs are or on the boxes.

Then you can e.g. Put in a glass.

What does sneak mean?

To sneak

So probably the shift key

A little tip in case you don't know:

You can place item frames where the signs are or on the boxes.

Then you can e.g. Put in a glass.

Sorry I don't want to lol