Updated to latest R13. Transparency masks stopped working in cycles render of blocks and exploded blocks. Switched to legacy Rhino render, no issue.
Works just fine here:
Try changing material type to Physically Based material if you’re using Custom materials.
Changing to PB worked. I’m able to select multiple textures to change them all at once too. Thanks
When 8.15 comes out you should be able to use custom materials again: RH-84849 Alpha in custom material broken