Server exhibiting absurd amounts of lag

My friend is attempting to host a Skyblock map on their Realms server. He is a switch player and our other friend plays on laptop, They are completely incapable of connecting to the realm, generally loading for a very long time before either the game giving them an error message saying they couldn't connect to realms, or they couldn't connect to the world and to try again later.

 

I also experience these issues but occasionally my computer does make it into the server, at which point I can walk around the world, however the game seems to only update once every minute or so, any blocks broken or chests opened will wait for minutes at a time to actually register.

 

We initially thought it was just lag but this problem has persisted for over a week now and at this point I'm uncertain how we should proceed.