On PTASK table, when Assignment Group changes, automatically it should set back the State to "New"

[AbdurRahmanSnow]

Good afternoon.
Requirement is: On PTASK table, whenever we change the Assignment group and save the record, it should set back the state to "New", if the States are in Assess or Work In Progress.
1) I tried using Client Script, but it worked only on Front-end and after record saving, it again sets back the earlier state and gives an error message as below:
Invalid state transition. Can not update from state 'Assess' to state 'New' with given values.

2) I tried to create a new State Model for PTASK for "New" State but it does not change the State to "New", upon Assignment group change.
3) I also created a Business rule that sets back the PTASK State back from "New", "Assess" and "Work In Progress", to "New", upon Assignment group change, but this too, does not work.

It always gives me the above error.
Please help, as I tried but nothing works. I would be grateful for this.
@Ankur Bawiskar @Dr Atul G- LNG @Viraj Hudlikar 

[AbdurRahmanSnow]

Yeah @Dr Atul G- LNG Sir, but the Problem team want this new feature implemented. 

[Dr Atul G- LNG]

Mate, I agree this is a client need, but this is a process violation. The purpose of a task is to track each team’s progress individually. If reassignment is required, then there’s no purpose in using a PRB task.

[AbdurRahmanSnow]

Hi @Dr Atul G- LNG 
You are correct. That makes clear sense.

Thanks a lot for the information.