Under what conditions is it permissible to sell an endowment whose benefit has diminished but not entirely ceased?

Primary text

If the benefit of the endowment has not completely ceased but has diminished, and another asset offers greater and more beneficial utility, the diminished asset should not be sold and returned to the beneficiaries. The underlying principle is the prohibition of selling the endowment, and the permission to sell is contingent upon necessity for safeguarding the endowment's primary objective from complete loss, provided that the objective can still be secured and utilized, even if minimally. However, if the diminished benefit reaches a level where it is considered non-existent, then its presence is treated as its absence.