https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/commits/bcedf28a1b6f4214539cd7c49b953a0e44039dcf#nms-patches/net/minecraft/world/entity/projectile/EntityEnderPearl.patch

Line 32:

+                    if (!teleEvent.isCancelled() && !entityplayer.connection.isDisconnected()) {
+                    if (!teleEvent.isCancelled() && !entityplayer.connection.isAcceptingMessages()) {

need to remove !

There could be more, just the first one I saw