Items from Shulker Box dissapeared

After accidentally coloring my Shulker Box to white color, and putting it on the floor caused the Shulker Box to respawn, and items inside despawning totally.

I tried immediately reproduce it by coloring another shulker and leaving only 14 andesite in it, didnt happen again.

 

I was playing offline alone, Im posting a link to a capture of the situation, sorry for the audio over, I was listening to some video.

 

https://www.youtube.com/watch?v=_75uk3v34Mg

 

0:20 is where it happens.