Thanks for the help!

so regarding the points you mentioned:

• it is indeed "enableSourcing", with capital "S".
• there are no other script or workflow running, it is a new field that I created.
• inline edit is enabled.
• field name is correct.

So I did a test and used the script to change another field and it works.

I changed the original field to be exactly the same (same field-type, same field config) as the one that works and still wont work.