The bedrock generation is Broken when generating chunks

When generating terrain often chunks will be missing or generated incorrectly eg. in flat world often there'll be 4 chunks (16x16) diagonally of just thin air no ground or bedrock. This also effects non-flat worlds. The problem might also be the cause of slow terrain generation so a potential solution might be to slow it down like on legacy editions with a giant invisible wall blocking the un-generated terrain.