Selection in "advanced" enum list will be deleted in certain scenario

When there are 3 drop downs, one determines the values of the other, the selection in the last drop down will be removed (even after being saved before) when two actions occurred to the rules in the row. Two actions includes changing the rule body, or saving the rule twice.

For example: I have the following statement:

in fact [field1] [field2][field3]

each of the field is presented as a drop down by using the advanced ENUM feature - 1 determines the values in 2 and the selection of 2 determines the value of 3.

After the value in field3 is selected, I can move on and make the changes in the rule. When the first change occurred, Guvnor remembers the values being selected in all 3 fields. But when another change is make (or simply save the rule again), the selected value in the last field (field3) will be forgotten.

Another scenario is that, after all the selections in the drop down are saved, we rename the rule (counted as 1 action), and then clicking save file will cause the lost of the selection in the last drop down.

Please note this is only happening to the last field. I did not go further and make the statement contain more than 3 drop downs.