Loading a custom structure doesn't load rails correctly

What is happening?

Probably Minecraft have bad days and don't want to load world/structures/structure.nbt/palette/(noname)/Properties/shape
String NBTData.jpg.
Unexpected is that the shape String is loaded normally for stairs that have also this variable.

How to reproduce

1. Build some rail art as shown on Step1.png. You have to build it in the directions of the world shown in screenshot.
2. Save it as a new structure using a structure block
3. When you load this structure first time, you will see that it messed up the rail art as can be seen on Step2.png
4. When you load it second time, it will load normally

Code analysis

Code analysis by Xcom6000 can be found in this comment.