it causes some problem since it affect the saving of this content type , This code is there for some other fields too . What will happen when i remove the computed code ? will it affect any other part of the content type ?
The code fetches the id of the node_project.
For example if the node's project field is set 'Foo' it will get the id of that row where it was saved. As its not clear from where $node comes whether its current loaded node or any other node. But it seems that in computed field you are storing the ID of the project
What I think is causing the problem is if project names are FOO and FOO_BAR the query will result both the ids which can cause to store incorrect ids.
You can simply remove the like operator and add equality.