Work Item Binding issue

Hi,

I have created a custom Workflow as copy of WS00500001 and added few steps for sending emails.

While sending email, I have to bind the current work item ID from Task to method. While binding, the variable is changing automatically on save. Below are the screenshots describing the issue:

Binding from Workflow to task:

Mail body:

Task:

Task Container:

Binding Task and Method (Which is needed):

But after saving this binding , If I go again and check this is changed to below and also with error:

Kindly suggest how to rectify this issue and how should I pass the current WI to method.

In the above binding, If I change the variable like below then there is no error. But after running I am getting the main workflow WI ID. So, the text is not coming from mail body.

Please help to rectify this error.

Thanks and regards,

Khushbu