SYMPTOM:
When a report contains an object prompts on multiple reports and each of these reports have the same prompt on same attribute but are saved with different default prompt answers, then re-prompting the original report does not change the default prompt answer corresponding to the report selected in the object prompt.
As shown in the following screenshot, object prompt contains 3 prompted reports with prompt on Region attribute and each saved with different prompt answers.

When you select rep1 and press Next, then you are prompted with default prompt answer for rep1 which is Canada as shown in following screenshot.

Now you run the main report, re-prompt it and select rep2 this time from the object prompt as shown below.

When you press Next, you will still be prompted with default prompt asnwer of rep1 again and not with the default prompt answer of rep2 as shown below.

CAUSE:
This is a known issue in Strategy Developer 9.x and 10.x.
ACTION:
Contact Strategy Technical Support regarding an update on this issue
WORKAROUND:
Instead of using the same (Region) prompt across all the 3 reports, create 3 separate copies of the same prompt and apply them to the three reports separately. In this way, when re-prompted and selected different report, the default prompt answer will change accordingly.