Web Portal - Error 500 while saving the request properties for a service item

Hi,
I added a Condition (query) on a parameter of request property related to a specific service element. 
When I create the request in Web Portal by proceeding to populate the properties, the first field becomes blank when we select the second field. Also by selecting the third field, the first field (the one on which the condition was applied) becomes blank.
When I save the request, I get an error in saving.

Everything works fine if no conditions are applied in parameter of request property.

Any suggestion?