I'm not completely sure this is what happens, but a lot of people from the community are reporting early disconnects due to timeout while connecting to a server. Everybody reports that increasing the loginTimeout from 900 to 9000 fixes this issue. That's weird, because it's already in seconds, so that's 15 minutes. Or is it? As far as I can tell, the code actually reads it in ticks, which means a client has 45 seconds to connect or they get disconnected, which is very hard to do on a big modpack.

Source: https://github.com/TheRandomLabs/RandomPatches/blob/1.16/src/main/resources/patches/ServerLoginNetHandler.js

I'll check this out tomorrow. 😄

You're right; I misdocumented the property. This is now fixed, and I've also increased the default login timeout to 1800 ticks (90 seconds).