There's an issue with requesting items from an Storage Controller w/ no inventories attached, or unlinked Controller Access Point.
If ..getSlots() is run on a system with no available inventories / unlinked access point, a server crash occurs.

So if any pipe requests items from an incomplete system, the server crashes as soon as the pipe attempts to run ..getSlots(). (Server crash happens when the item is requested).
And when AE2 attempts to build an item cache on an incomplete system, it runs ..getSlots() as part of this. (Server crash occurs upon loading the area).

Noticed the issue on ATM9, which has the latest version of Functional Storage available for 1.20.1 on Curseforge, v1.2.11.

Server Crash Log:
https://mclo.gs/qxtcbtc

Issue typically occurs when players are going to move their storages, but don't break the pipes interacting with the Functional Storage system before doing so.