"assigned By" value is not updated in custom table
I have an issue in PPM that I created an item in PPM and assigned a parent to it and then I removed the assignment and made the assignment again then what I see is that "assigned by" value is not updated neither in foreground nor in background in custom table.
Screen shots of both the cases are given below:
Can you please suggest me what is wrong here and how we can get the "assigned by" value back .
Thanks in advance for your response.