Minecraft version:
1.12.2
Betweenlands version:
3.3.8

Minecraft forge version:
14.23.3.2688

Singleplayer (Not tested yet on multiplayer)

Installed mods:
nethergoldore 1.1.2
Optifine HD U D1
overpoweredarmorbar 0.2.1
torohealth 1.12.2-11
twilight forest 3.7.424
VanillaFix 1.0.0
worldedit 6.1.8
advanced xray 1.4.1

The problem:

When inserting the proper materials such as life crystals and sulfur in the Animator, they remain fine. After a while, however, the trouble begins when the items are left too long in the animator. After certain period of time, the items vanish into thin air! I am not sure what causes this glitch (chunk loading, render distance, invisible item timer, etc), but it sure does remind players to remove their items after using the Animator.

Steps to do:

1. Put a Life Cystal and/or some sulfur in the animator
2. Close the GUI and wait a while. Maybe take a long walk. Or look for another Life Crystal, since you know that the original one in the Animator has vanished into thin air.
3. Come back to the animator.

Expected result:

1. Open the Animator's GUI and look to see all the items still intact!

Actual result:

1. Open the Animator's GUI and look to see all the items GONE! (I am not sure if the items INSIDE the orange box disappear)

Pictures:

No pictures provided, it is a glitch that can be replicated easily.

Note My render distance was 5 at the time, I am not sure if this triggers the glitch.