This is a failure of a Seej Masonry Bloxen.
I stuck an LED inside it to highlight the software-generated infill pattern.
ReplicatorG does this cool thing when preparing the model for printing, generating a honeycomb pattern for large solid volumes. Presumably this feature was designed to save plastic and printing time.
It’s like magic the first time you see it in action.
This is a PLA print at 10% infill. One hundred percent infill would print a solid block of plastic.