The Bug

Ancient debris blocks being pushed and pulled by sticky pistons can be destroyed by explosions.

Steps to Reproduce

1. Create a creative world with cheats on, set its difficulty to hard, and start playing.
2. Build a wall (for example, 6x6x1) with sticky pistons and put ancient debris on each of their heads so the pistons can push and pull the ancient debris wall of the same size.
3. Build a redstone clock circuit. It can power the pistons with redstone signals so they can extend for two redstone ticks and retract for two redstone ticks, and so on. Make sure the whole circuit is on the pistons' side of the wall because explosions will be created on the other side in the next step.
4. Create an explosion near the wall on the ancient debris' side. To create an explosion, you can
   • Summon a creeper with creeper spawn eggs and ignite it with a flint and steel.
   • Place a TNT and ignite it with a lever.
   • Place an obsidian and an end crystal on top of it and hit the crystal by hand.
   • Summon a wither with the command

     /summon wither

     and kill it immediately with the command

     /kill @e[type=wither]

Observed Results

When the piston wall doesn't receive the clock signal, the ancient debris wall is stationary and can protect itself and other blocks behind it from being destroyed. 
However, when the piston wall is powered by the redstone clock and moves the ancient debris back and forth, there are chances that the explosion destroys part of the moving ancient debris wall and some other blocks behind the destroyed part.

Expected Results

The ancient debris block has high blast resistance and is immune to normal explosions. It should not be destroyed by the explosions mentioned above, no matter if it's moving or not.

Video

Ancient Debris Explosion Test.mp4

Contraption Screenshot

Minecraft World

Ancient Debris Explosion Test.mcworld

Notes

• The screenshot and the video posted here are captured in the attached creative Minecraft world.
• The bug also affects the ancient debris moving vertically in the current version.
• In 1.19.51, one of my contraptions used ancient debris as movable blast-proof blocks. They could block the explosion when they were being moved by pistons; the contraption worked flawlessly. So, I think this is a bug introduced in the 1.20 versions.