My server keeps shutting itself down (not crashing). What can I do to diagnose the problem?

I've been running a server with this modpack for a while. The server is running Java Edition 1.17.1, Fabric 0.14.6.

Ever since updating the modpack version (and the server) past v3.2, however, the server keeps shutting itself down. It's not crashing: there is no crash report, and the game works just fine once I reload the server. There is no common activity, like loading in chunks or using specific modded functionality, that precedes these shutdowns.

The mods that have been added to the server since the issue began are:

- Lithium

- Phosphor

- DimensionalDoors

- Clumps

- Extended Armor Bars

Are any of these mods known to cause this self-shutdown issue? How could I go about diagnosing the issue?

Here's a log from a self-shutdown incident:

Fabric server log [#GSvTrJS] - mclo.gs

The server in question is Greyhawk_Block.aternos.me.

No one joined the server at that time or on previous occasions. This issue has occurred when multiple people are online, though.

The log I sent is from an instance of the issue. That's the problem: the server just closes with no explanation.

Oh, interesting. Thank you for telling me!