With a beacon built at y=-60 the beacon buff only applies to me properly at positive y values. standing with my character at y=-9 the beacon buff stops applying even though I am closer to the actual beacon every block down I go, seeming that the beacon buff is only looking for players within 8 blocks of y=0 to apply the buff, and ignoring them below it.
Please attach screenshots or video of the issue with the debug screen (F3) enabled.