Hi.
Used COPY on a group of blocks.
Used PASTE and tried to place the group at a desired location and couldn't. (LMB)
Used ALT, to try and specify where the paste should happen. (LMB)
Couldn't paste still, (got a red block "Can't place here" indicator).
When I MMB clicked over the visibly EMPTY area near my ship, where I wanted to place the copy, I found multiple "invisible" blocks, that could be deleted like any other. All I could see was the block edge Hi-lite, when clicked on.
The invisible blocks could also be deleted in any order, without needing to be "attached" to another block.
Didn't get a screenshot, but will try to reproduce again and send one.