Archas disappearing

[Twackersixx]

I am playing on PS4. I'm playing on single player, non-dedicated server. My husband and I both are having a problem with the Archa dinos. We each are playing single player on our own PS4. The problem is the archa's are disappearing. I created a room surrounding a tree. Completely inclosed. I leave for a while and come back and the archa's are gone. I originally just put a fence around the trees and they disappeared so then I made a completely inclosed room and they are still disappearing. My husband is having the same issue. I believe there is some sort of glitch. Also, my husband had a rock elemental that he had for a while, but it disappeared, too. Another thing to note is that I had 2 archas in a different location, but they were not with the correct trees and they never disappeared. They only started disappearing after I moved them to a place with the correct trees to make sap.