I've implemented that solution you suggested and it works now. I just had to remember to clear the value_store after the go_back() call so that it didn't execute on the next form open and save with the default data action buttons.
It might be because I have been jumping around all over the place in and out of the builder and my session history is a bit muddled, but I had some strangeness with the go back data actions intermittently, it seemed to go to different forms that I didn't remember accessing ('all calls list' as an example). Using a test user not in maintenance mode rather than the builder admin its been consistent.
I tried using
app.open_form('0849e7ad-a803-45ab-86ba-60afb5d1a5a7',0,false,false,0,0); to hard code a return to my overview screen UUID rather than using the go_back() function, but that seemed to only open the main home screen app dashboard instead.
Also noticed an occasional bug with go_back and modal forms. If you open a full-screen form from a list and then from that form open a third popup modal, and click go_back, it jumps all the way back to the list skipping the parent form.
Cheers again for all the help, I've come a long way in a little over two weeks! We're live tomorrow.