Bumping this thread as its still an issue and still stopped me getting my platinum 😢
Thank you @denisdr231 - but as I mentioned in my original post i already have this priorite shard in the Forward Control Tower.
There is a scavenger droid in Basalt Rift - from what I have read the bug is that if you don't kill this droid on your first time through the area it will never drop the priorite shard on any subsequent visit to the area. All the other scavenger droids vanish after you kill them and pick up whatever they drop - but this one in Basalt Rift keeps spawning but never drops.
