I found this in my Server Log.

[02:09:56] [Server thread/INFO] [nucleus]: Starting QuickStart Module Loader version 0.10.1 subsystem.
[02:09:58] [Server thread/ERROR] [immersiveengineering]: Compat module for tconstruct could not be preInitialized. Report this!
[02:09:58] [Immersive Engineering Contributors Thread/INFO] [immersiveengineering]: Attempting to download special revolvers from GitHub

Report this!

Mission done :)

SpongeForge 1566 1.12.2
ImmersiveEngineering-0.12-81

Do you have tinkers in this instance?

I just tested, this did not happen to me. I tried both Forge 2673 and recommended (2655). There has been a second "report" of this on the IE CF page. I used the same IE and TiC versions as specified in that comment, both downloaded from CF.
@djdanby Could you try without SpongeForge and upload a full mod list?

I'm the reporter on the IE CF page. The notable side effect is a lack of IE materials as tinker's tool materials.
Here is a full modlist (just a dump of the files in my mods folder... if there's a better way to get a list, I'll be happy to do that): list.txt

As a bonus, here's a full log file containing the error djdanby posted:
latest.log

Edit: Forgot to add, I'm using the recommended forge version: 14.23.3.2655.

No i do not use Tinkers. Here is a screen from my mods: (https://picload.org/view/dodwlgpa/modlist.png.html) I can not test it on my server one spongeforge. that would probably swirl some settings through each other. I do not want to risk that.