Suggestion:
As long as the fee for the shadchan is in escrow, it should remain there until the 5th wedding anniversary of the young couple. Upon the 5th anniversary the shadchan will receive the fee; thus ensuring that the shadchan will work to find a suitable, lasting match.
A shadchan may offer to provide counseling services to the young couple should they ask for it. As the shadchan would have a stake in the marriage lasting 5 years, it would be to the chadchan’s advantage to help.
A farmer who plants a tree may have to wait years until the tree bears fruit. Perhaps shadchans should also have patience while the efforts of their matchmaking bears fruit.