It seems there is a bug with the reward of the heavily protected percursor artifacts.
As you see on the image bellow it states there was a vast quantity yet only gives 1 Elerium which is pitiful and to investigate this anomaly lost 12 spaceships. Surely there must be something wrong.
Also this is the first time I find something in a protected anomaly. Usually they are completed by another civilization as per notification.
Please find attached the save file just at the start of the turn before the reward is given.