Sinkholes going down to lava level are generating in large lakes in Bedrock Edition, often with structures that don't even belong to the biome, or a large stack of aquifers that reach the height limit above the sinkhole.

How to reproduce:

Load up a world on bedrock edition with either of the seeds provided below, and use the /tp command to teleport to the coordinates provided in the pictures. 

Observed results:

A hole going all the way down to lava level was formed in the middle of the lakes in each of the seeds, some of the holes having a stack of aquifers going up to the height limit like in the 1st and 3rd seed, and there were structures generated in the holes, and some of the structures are not even in the correct biome, like in the 1st seed, the ocean monument was not even in a deep ocean biome, as the nearest one was over 1700 blocks away, and in the 2nd seed, the woodland mansion did not even generate in a dark forest (or 'roofed forest'), as the nearest one was 800 blocks away. Additionally, water in invalid states (floating) was seen with the ocean monument in the 1st seed, and there was a buried treasure chest (under the hole as well, and not in a beach biome), that overrode the bottom most layer of bedrock in the 3rd seed. 

Expected results:

A lake, without a hole in the middle, without structures or aquifers, would generate. 

Seed used for 1st and 2nd picture (1st seed): 225168984193282

Coords: -13, 63, 97

Seed used for 3rd and 4th picture (2nd seed): -346758088935028527

Coords: 398, 63, 538

Seed used for 5th, 6th, 7th, 8th and 9th picture (3rd seed): 5106449350243512140

Coords: -34, 63, 32

Note that the yellow potion particles in some of the pictures is due to the night vision effect, to better see in the dark.