In T166337#2345059, @ViTalPulse wrote:

Something that I do notice is that when the delay exists it can happen that both the AI as the players (without GM mode) already see the entities. (spawning a US and FIA force with delay can start a gun fight without us (GM) seeing them)
Also when a GM leaves the game and comes back in the delay can sometimes be gone, this is not consistant and only works 5/10 times. But they do often see the units that are invisible for the other GM.

These budget settings seemed to help, or I got lucky:

Was able to reproduce with PeerTool.

I did find a helpful error message way before the kick, and managed to resolve the issue, so this can be closed.

Server logs at time of event

Mods config on server

Meanwhile in Singleplayer

Logs