[BUG] Stateless form custom button doesn't display updated field value

[BUG] Stateless form custom button doesn't display updated field value

Can anyone reproduce the same bug?

// Stateless form
- Single line field: Field_1
- Single line field: Field_2
+ add custom button "test"

// Script
On click of "test"
input.Field_2 = input.Field_1;
alert input.Field_2;

// Result
alert shows the script is valid and display the expected value
Field_2 is not updated with the expected value.

The field_2 is clearly been updated as the alert script output the correct value, but the UI is not been updated by the first script.