biobots shutting down inside a neutronium tile and are inaccessible

I am not sure of when this occurred or what caused it.  For some reason two biobots shut down inside a neutronium tile so they are not retrievable.  Also it seems strange that it occurred twice in the same tile.  That tile is located in the bottom right corner of the cold asteroid. .It is not a location that I would send them to do work because there is nothing interesting there.

Hopeful Acropolis.sav