Flex Repeater not working on preview mode

Hi Team,
I have a user dropdown, dropdown change creates an array and assigns to custom property (array type), It is binded to instances property in Flex Repeater.
Issue 1
On preview mode, when I change the dropdown Flex repeater is retaining the old values, but when I switch to design mode it shows the correct current value.

Issue 2
First drop down change creates 3 instances, and second dropdown created 2 instances.
But on preview mode, Flex repeater is retaining the old 1st item, only 2nd one is getting updated

In both scenarios, I checked the custom property it is changing correctly though.
Please share your thought.

Thank you
Manu