The bug
Beacon beam can only extend 256 blocks, despite the new height of -64 to 320. To replicate this, place one beacon above Y=64, and one below Y=64, and then fly up. Once you get 256 blocks away from the lower beacon, the beam will disappear, while the other beam remains.
Linked issues
is duplicated by 1
Attachments
Comments 2
Added pictures. The quadruple beam is from a beacon placed at bedrock. At y=192, it is no longer visible. A beacon placed at y=192 will continue above the built limit.
Panda4994
This relates to MC-151747.