When setting the BeamTarget of a end crystal to above around Y:2000 on a server, the target overflows and instead points towards around Y:-2000.

I have tested this on singleplayer and multiplayer, and it does not affect singleplayer (other than for the unrelated issue in MC-217030) 

Command to replicate: 

/summon minecraft:end_crystal ~ ~ ~ {BeamTarget:{X:0,Y:2060,Z:0}}

The NBT data also seems to suggest that it should be pointing towards Y:2060.

/data get entity @e[type=minecraft:end_crystal,limit=1,sort=nearest]