[8.0.0-PRE-RELEASE-5] Lava generation offset by -1 block (y-axis)

[Former user]

Plugin version: 8.0.0-PRE-RELEASE-5

Spigot username: MadByte

Issue: Lava seems to be generated one block above the target position. (see screenshot) No edge cases, got this every single time I generated a world. Using paper-spigot (tried default spigot as well). Paper version: git-Paper-316 (MC: 1.13.1) (Implementing API version 1.13.1-R0.1-SNAPSHOT)