The inherent danger in Prom position in W and F/trot ( moreso in waltz ) is the poise that needs to be established between the feet .
When judging, I frequently see the "early collapse" of the fwd foot, caused by the fwd poise and balance not controlled between the feet . .
The suspension required in Waltz, is often affected by weakness in the foot/ankles-- the F/t trot has a similar problem-- but-- this having a more free flowing fwd dynamic, presents a new set of problems --
not " collecting the weight as the step continues thru to its next destination , can very often be a major contributor to this action of early lowering-- particularly in W.
As an exercise-- try keeping your weight divided between the feet ( with suspension ) on 2 AND 3 -- learn to lower and " swing thru from that position ( the lady obviously has to contribute in a same manner ) the figure that follows can also determine the exit speed .
Your particular problem might have other factors, that should be taken into account .
analysis in this format ,is like describing an elephant to a blind person .