Hibernate many to many removing entries in join table while update owner table

Hibernate many to many removing entries in join table while update owner
table

I am trying to update an entity which is having many to many relationship
with another table.
@Entity(name = "coaching")
public class CoachingEntity {
@ManyToMany(fetch = FetchType.LAZY, cascade = { CascadeType.REFRESH })
@JoinTable(name = "coaching_field", joinColumns = @JoinColumn(name =
"coachingId", referencedColumnName = "coachingId"),
inverseJoinColumns = @JoinColumn(name = "fieldId",
referencedColumnName = "fieldId"))
private Set<FieldEntity> fieldEntityList;
Now, when I update CoachingEntity, hibernate is removing entries from
coaching_field table (many to many join table). I have searched in
internet (JPA update many-to-many deleting records) but I am not able to
find the right approach. Even in JPA many to many merge on the owner
triggers delete on join table, I tried his recommended approach where he
used set but I am facing the same problem. As per
http://stackoverflow.com/a/1078295/2116229, do I need to override equals
and hashcode?