Modpack version
Enigmatica2Expert-1.80

Issue
The server OP uses the My Server settings in the FTB client settings to modify the nickname resulting in the Cyclic Extended Inventory being cleared.
The specific operation is as follows:
Press E to open the backpack, click Client Settings at the top left of FTB, then enter My Server Settings, then modify Nickname, and then Cyclic's Extended Inventory is cleared.
(machine translation)

Logs
None

Thank you for the report, I will investigate the issue.

I don 't know what happened. I asked my friend to try. He changed his nickname and then changed it back. The disappeared items reappeared, but I couldn' t.

I'm sorry but it's a bit too circumstantial to try and fix.