After searching 5 days for ancient debris, I can say for sure I do not have any. I used beds to explode areas at y=14 in the nether and since I suspected some bug I switched to creative mode and exploded big areas with tnt. Still no sign of any ancient debris. must be a bug. also this world of mine when first loaded on the snapshots had deleted all my llamas, sheep, dogs, cats and horses in and around my house.