Structure blocks loads 9 ender dragons when only one is saved

The Bug:

When saving ender dragons with structure blocks, ender dragons are saved nine times, which causes the ender dragon to be duplicated.

Steps to Reproduce:

1. Download the provided structure block .nbt file that contains an empty structure that has one ender dragon within it. mc-257728.nbt
2. Create a world and place the .nbt file into the generated\minecraft\structures folder.
3. Place down a structure block with the appropriate data already inputted into it by using the command provided below.

   /setblock ~1 ~ ~1 minecraft:structure_block{ignoreEntities:0b,mode:"LOAD",name:"minecraft:mc-257728",posX:1,posY:0,posZ:1,powered:0b,showboundingbox:1b,sizeX:29,sizeY:13,sizeZ:29}

4. Open the structure block and click the "LOAD" button to load the structure.
5. Take note as to whether or not structure blocks load 9 ender dragons despite only one being saved.

Observed Behavior:

Structure blocks load 9 ender dragons despite only one being saved.

Expected Behavior:

Structure blocks would load one ender dragon if only one has been saved.