NOID Phal Repotting Trauma

[sapphirerose]

Meet Dave. My NOID Phal from Aldi. I repotted Dave on 10/30/2016. At that point, he had decent roots and seemed very healthy. I used RePotMe Montery Dark. Though I think I got too much of the moss since it was the top of the bag. I noticed Dave tipping out of his pot this evening. Most of his roots have died. Any ideas? I'd like to work out why my repotting is killing my Aldi Phal before I repot my new Phal equestris plants.

Should I repot him entirely again or just try to secure him instead