The recent update for Sparklite released on January 10th, 2020 Friday fixes the bug of the last Beat not spawning on the map. Now the last Beat along with the last two achievements are attainable. Once you obtain the last Beat, the song is pretty amazing as well!
If you have trouble finding the Beats, the map will reveal how many you have left to find:
Yellow Beat – Acid Bog
Red Beat – Vinelands
Purple Beat – Titan’s Ridge
Blue Beat – Goldenwoods
Green Beat – Sinking Sands
Hope that helps and happy hunting!