on the lan, high levels of jump boost ground you
what I expected to happen was: jump boost works normally, levels 0-127 increase jump height, 128+ prevents jumping
what happened was: on several different worlds, jump boost levels 95-127 allowed jumping, but then teleported the player back to the ground. this only applied to players other than the host, and applied across worlds, and with 2 different hosts. hitting the grounded player allowed them to jump once, then they were stuck again.
to reproduce: make a world. LAN it. have another player log on. give everyone jump boost 127. the host will be able to jump, but not the other player.