There are issues with beacons in the new snapshot (21w06A). Due to the new height limit, beacon beams cannot travel all the way from y=-64 to y=320. In the screenshot with two beacons beams, one beacon is at y=-64, and another at y=192. The y=-64 beam is visible. In the next screenshot, it is gone. However, the y=192 beacon is visible. The beam from this new beacon travels all the way to y=446. It seems that beacon beams travel about 255 blocks, regardless of where the beacon is placed. Instead, all beacon beams should go up to y=320, and stop there.