Parasolids are 'dumb' solids, the mates are lost.
Versions are not backward compatible.
Create a step file of the assy, open in the other SW version, then re-mate the parts.
Parasolid is the "best" native way to downgrade.
No export (x_t, step, iges, ...) preserves the mates.
If I remember correctly when you import a Parasolid the components come in "fixed". In order to move them you need to unfix them.
Edit:... or float them is what I meant.