Same issue as reported in MCPE-190845 Named Creakings may not continue to exist on world reload, so after several reloads they may all disappear.
Was reported to be fixed in https://feedback.minecraft.net/hc/en-us/articles/36236281562637-Minecraft-1-21-80-Bedrock yet still is a problem and the MCPE-190845 remains “fixed” even when clearly not fixed.
Linked issues
Comments 2
I also opened MCPE-218667 for this same issue.
Same issue here on 1.21.81. I spawned a new creaking, name tagged it, then exited and reloaded the world. When I came back in, the creaking was gone.