Hmmm

+
To be honest, I did not deleted that floating grid to verify so it may be a tiny bit of Voxel tho the SE Programmer replied saying they were able to reproduce the bug.

Hi Sevyrs,

you may give it a try and add your testing to the Portal report, the Workshop item and the Portal Bug Report are in this discussion :

https://steamcommunity.com/app/244850/discussions/1/3826415019287292802/

I ask because this image shows the three blocks floating unassisted so there may be voxels within their space that is locking them in place.

Very strange. At any point, does the subgrid clip into the voxel terrain or is there a floating voxel that was present when you were building that ended up causing the grid to be defaulted to station? Have you tried disassembling the entire subgrid and making sure you didn't miss anything?