Any items in the crystal chest that have 2 stacks ( 64 x 2 ) are not rendered in the block model that shows the contents of the chest.

THEN

When you have 2 different items with 2 stacks ( 64 x 2 ) each the client will crash producing this crash log here:
https://pastebin.com/JmbgNQvd

The crash happens as soon as you drop the second stack of the second item in the chest as seen below
https://gyazo.com/96e182586ce40137b1776a1a7f2d65e6

Fixed in the latest commit, Don't know why git didn't close this :P