it appears there is a similar bug in play here, i had created 2 XR-1 robots and set them next to an Atomic Compressor left them to work and collect the materials etc, but i had to quit the game to see the online manual to b/c i couldn't remember how to make another compressor.
So i placed a blackrock-blue block on top of the compressor then hit ESC to quit which also saved the game, when i returned to the game after viewing the manual, the XR-1 robots were gone along with the massive 10x10 pits they had excavated, the materials in my inventory remained the same along changes i had made to the surrounding area, just the robots and their work areas had dissappeared, there was nothing in the compressor b/c the robots hadn't finished their cycle yet.
could this be a problem with the atomic compressor or should i use F5 to manual save first before quitting the game?