Thanks for trying it out! This package hasn't been updated for Godot 4.3 yet. They've just recently added TileMapLayers and are deprecating TileMaps. I plan to update this package for the latest version of Godot in the next month or two.
Regarding the specific bug you are facing, I don't think that's your fault, I also remember having an issue putting down the shingles a long time ago. I don't know if it was for the same reason.