If you generate a custom world with custom height values, the bedrock floor does not generate, which means there are holes leading to the void. See attached pictures and json file.
MC-216135
Bedrock floor does not generate in worlds with custom height values.
Resolved
Invalid
0
This is not a bug; you have entered the value for "bedrock_floor_position" incorrectly. This value determines the offset of the bedrock layer from the minimum y-value ("min-y" under "noise") of the game's noise generator, not its absolute position on the y-axis. Your value of -512 is making it attempt to generate 512 blocks below the bottom of the world, which is obviously impossible. Set it to 0 and you should be fine.