If the adjudicator has determined that there is no claim against the property and the only way of claiming against you is as an unsecured debt, that sounds clear. Either your ex hasn't clocked that or he is trying it on (again).
If he hasn't clocked it, he presumably believes that raising the claim again will in some way delay or prevent you selling - because any buyer (well, their solicitor) will uncover this and fear it will turn into a delay. But I don't see how that can work, if what you say the adjudicator said holds true.
The other way he might be thinking about it (if he has clocked that he has no claim on the property), is that he knows house-selling is a stressful business, and he might just manage to increase the pressure on you enough by re-raising the claim again that you crack. Especially since he will presume that once sold, you will have a source of funds.