Modpack version
Enigmatica 2: Expert v1.65d

Can the issue be reproduced?
Yes

Logs
I reproduced the bug multiple times in the last five minutes, but the logs for the last two hours are just server backups, so nothing about this shows up in the logs.

Issue
Apply a [Random Things v4.2.7.1] Time In A Bottle item to a [FastFurnace v1.3.1] Furnace (the one that looks like a vanilla furnace) while that Furnace is heated by an [Immersive Engineering v0.12-89] External Heater.

The furnace will eventually 'blink' off (sometimes rapidly like it's in a rave), deleting input and output contents of the furnace.

Two applications of the bottle risk creating this issue. Three applications almost guarantee it. Four applications of the bottle definitely guarantee it.

I'm providing links to the issues I've opened in the respective mods just to help everyone out.

Enigmatica 2: Expert
Random Things
FastFurnace
Immersive Engineering

Thanks for letting me know.

Why is this closed ?

Because the developers of IE and FastFurnace won't fix it, there's nothing more we can do about it I'm afraid.