Solutions to infant constipation due to thickener+formula

Our 5 mo old recently had a swallow study and it was determined she needed thickened breastmilk to keep her from aspirating while eating. That gel mix thickener is going into breast milk that's fortified with formula powder to help her gain weight. All of this was great until it started turning to cement inside her and leading to severe constipation.

We're currently stuck in a cycle with our medical team of clearing her out by cutting out thickener and fortification, then adding it back in, and days later we're back where we started: inconsolable, bloated, sad baby who won't eat.

We've tried miralax and laculose (both medically prescribed), neither seems to be able to overcome the issue. Anyone else had this and how did you break the cycle!?