When flying in the End above the build limit there appeared to be something like a server/client desync. The the player ceased to move in either the x or z directions and could only maintain elevation with rockets. After some time the player began moving again but and when I reached the center island and got under the build limit the player was transported to y=0. At the time this occurred the server console reported the following:

Server thread/INFO Skipping update from removed player 'class_3222['lukei4655'/210151, l='ServerLevel[Catholic Land]', x=0.93, y=61.73, z=2.12, removed=CHANGED_DIMENSION]'

Another player experienced this same event on a previous date. The common action was flying above the build limit in the End.