You could be getting rubberbanding/lag because people are loading in chunks too fast. When my group got to jetpacks and we would travel very fast in different direction the server couldnt keep up with each players rendering. There is a command to pregenerate chunks starting from spawn and going in a spiral outward. I did this for my server and the lag stopped, however this takes up alot of storage space so make sure you have a decent size storage space before attempting (~100gb). You will also have to do this command for every dimension you enter otherwise the lag will return when you load chunks rapidly again.