The issue is described by a simple example.
Create a Promptset with e.g. only one Text Field and give it a default value:
<Please see attached file for image>

Add this Promptset to e.g. a Job. The default value is shown:
<Please see attached file for image>

Close the Job and edit the Promptset again. Change the default value of the Text Field:
<Please see attached file for image>

Open the Job again and check in the task Properties the Promptset. the default value is still the old one:
<Please see attached file for image>

This is wrong. The new default value should be shown.