Not a solution but the anwer on what is wrong:
Detected ALOS products (as provided by ESA) are not supported in SNAP, by now. That means, SNAP doesn’t know how to handle the data structure correctly. I’m afraid, opening new topics won’t change this.
What you can do is asking the developers (@mengdahl, @junlu) ALOS data from ESA will some day be supported by SNAP.