Site Content Type with QuickParts to be used across site collection

Question

I've been struggling to create a library which uses several site content types to create forms/documents using metadata of other lists in the same site.
I've looked around the site and this question seems to be exactly what I am asking.
Use of QuickParts in Word Templates in combination with Site Content Types I've got 1 root site and several subsites from that rootsite.
I've created my word template, uploaded to my library A, resided in subsite 1, and downloaded the file again to enter the quickparts. Then I upload this new file as my new content type in my rootsite, and it works when I add that content type to library A. All fields are updating as their respective column updates. But then when I add the same content type to my library B, resited in subsite 2, all the quickparts stop working...except for one...and for the life of me I could not figure out what was so special about that one field...it is just a single line among a few other single line fields.

the answer by Oskar Lundgren seemed promising but I am not sure where that piece of code he provided should go...I only have sharepoint designer, is it still possible to overcome this SourceID issue?

Answer 1

So I'm not a big programming person...and didn't really know what to do with this SourceID issue...but I figured that if every new column has a different SourceID then I'd just need to use one common column to avoid having different SourceIDs

Hence, I created Site Columns in my root site, and then in the libraries in my subsites, I simply use 'Add From Existing Site Columns' instead of 'Create a New Column' for all the desired fields, worked perfectly without code~