Crash w/ Structure Blocks

Minecraft v1.12.2 Forge v14.23.5.2838 EDX Multipart v1.1.1 McMultipart v2.5.3 Capsule v3.2.103

If I add a double slab to a new structure file using the structure block, the game will crash when using structure blocks to place the new structure.
EDX Multipart converts double slabs to McMultipart blocks, which seem to crash with Structure Blocks.
This also means that McMultipart blocks are incompatible with the Capsule mod, as seen in the post I posted here: Lythom/capsule#15

amadornes / MCMultiPart