Update related field Source Module 1:M

[shawkatmarrouf]

I'm trying to update a field on a module which has the 1:M Field based on on a related field from the other module of the M relation.
Example: I use workflow task "Update related field" to update a field in Projects based on a field of Project tasks and it works, but I wouldn't work when I'm trying to update a field in Project Tasks based a field in Projects.

Is there any idea how to make it work?