Every time I load in (except for a few lucky times) I get insta kicked out again by the stupid vanilla loading world timeout (had that before on other 1.12 modded servers). I have a slower connection so I can't help it, but I usually have few issues once actually loaded.
This mod can remove all that annoying junk though (you can set the timeout really high and it doesn't cause issues). It can be installed on server only side. Another server I play on uses it and it works great.
https://minecraft.curseforge.com/projects/randompatches
EDIT: if it works out, put it on all your severs (even works on vanilla)
Login Sheild would also be a nice companion (though random disconnects should be less of an issue with the above installed)
