AccessType.PROPERTY and setter problem on Map

Ok I made some debugging and what a surprize when I discover that during persist method when the setter is called by reflection, the value argument become empty???

Seriously, there’s something I don’t understant. Then I try to wrap my the map arguments in an inner-method map and it’s work???

Working example:

    public void setMyEnumsByProperty(final Map<MyEnum, Integer> myEnums) {
        // if not wrapped, the map become empty after clear is called!!!!
        Map<MyEnum, Integer> temp = new EnumMap<>(myEnums);
        this.myEnumsByProperty.clear();
        for (MyEnum myEnum : temp .keySet()) this.myEnumsByProperty.put(myEnum, temp .get(myEnum));
    }