I think you also need to add the 'schema' name in the @JoinTable, as you have a custom schema for your Entity Table, otherwise check the 'public' schema for the 'join table'.

"spring.jpa.properties.hibernate.show_sql=true" - is useful property to check what queries Hibernate is issuing to the database.

    @ManyToMany(cascade = CascadeType.ALL)
     @JoinTable(name = "drug_symptom", schema = "meds",
    joinColumns = @JoinColumn(name = "drug_id",nullable = false),
    inverseJoinColumns = @JoinColumn(name = "symptom_id", nullable = false))
     private Set<SymptomEntity> symptoms;