Can someone diagnose this phal.? Weird black color on the roots.

[K.O.]

This is a phal. tying shin baby smile. I dont know whats wrong with her but ive been fighting with her ever since i brought her. I had to repot like 4 times because she was acting up in the medium, or becoming dehydrated. I think shes growing more roots but the top roots are black but still firm as you can see. Also shes dropping another leaf and the aerial roots are shriveled up to a certain point which is weird.