In ArcGIS 10.5 there is a tool for attempting to recover a corrupted file geodatabase. I have just had to use this and was able to recover the data but not the relationships that I had built. It does state in the help that Complex data and relationships will not be recovered.
But I noticed that it failed to recover any metadata. The information that I had lovingly put together was lost. Unless ESRI think metadata is "complex data" it would be a good improvement to this tool to recover the metadata as well as datasets.