Description of the issue:

Wooden Storage Crate & Reinforced Storage Crate too
Filling storage crate and breaking it in survival, then changing gamemode will result in vaporizing of Storage Crate's contents. It happens when you are having Crate in inventory while changing gamemodes and also while breaking Crate in survival, advanced item informations showing zero NBT Data so its basically behaving like "empty" though there shall be contents.

Crashlog:

No Crashlog generated but got this inside .log file:
https://pastebin.com/FYfu6hD5

Versions & Modlist

Forge 1.12.2. - .2768; Immersive Engineering 0.12.89.jar
Also using SpongeForge latest build

MinecraftForge/MinecraftForge#4580

Thats the issue.

Had that problem twice. Went and checked the change log but did not have the leak problems errors.
forge-1.12.2-14.23.5.2808
ImmersiveEngineering-0.12-89
I'll experiment and report back
UPDATE: I am not able to set up a server so this test is in singleplayer. With just forge and IE I do not get the error, so unless it is specific to a multiplayer [off site server] problem then for me it has to be a mod conflict. I'll keep researching on my part and try setting up a server to test against.

That is an issue of forge, nothing that can be done much. If i remember right, it is an issue with updating/syncing inventorys.

Thhank you :) @bookerthegeek