Please try this using SPPB Module RC2, create a Row then add a "container" class so the content will be rendered in the middle. Without the "container" class, the module containt will be rendered full width. Then add a Row lock inside the first row. Add a Heading block in each columns. Save and view the page. You'll get an error:
https://monosnap.com/file/WdLDydVdeL1KDXFjthjzUFTSYLQfa2
I tried this with SPPB Page and I don't get the same error. The error only happens with SPPB Module.