Two issues. The first, the disowned Deuterium asteroids within a system that I've conquered won't let me build a mining base on them. I also used tractor ships to try moving them farther out of trade range of their former owner, and through warp gates. Other asteroids seem to allow me to build on them just fine, but Deuterium ones don't. I now have a collection of them that I can't seem to use.
Second issue: After I scanned a debris piece, an event asked me to choose between being given the location of a number of (some kind of) facilities, or some immediate reward. I choose the facilities, but nothing seemed to happen after that. I presume that something was supposed to happen. The debris was located in a system that, I think, appeared after the game started and came about from the diplomatic event, which an AI won. The system was full of neutral fleets.
I haven't played for long, so these may not be bugs and the fault may be mine.