I stumbled across an interesting bug with Precursor Anomalies. I had attacked a Precursor Anomaly with a fleet that I thought had an Explorer in it and defeated the defenders, but I did not get the "prize" from the anomaly. Now, I can move a fleet to the cell containing the Precursor Anomaly and nothing happens. Here is a screen snapshot of what it looks like (note that under "Specials" it says "Survey Ship"):
