Some of the lava blocks in ruined portal structures are not source blocks

Some of the lava generated in ruined portal structures are not source blocks.

Seed: 8933689684201835290

Coords: /execute in minecraft:overworld run tp @s -983.25 71.00 -11165.25 -577.20 19.50

Look under the portal.

 

Another example:

Seed: -182990544726772226

Coords: /execute in minecraft:overworld run tp @s -378.07 65.42 -364.20 -425.56 60.15