Ok so I have dug around now for a few hours and tried a few different things to try fix this. However, my changes I am making in the builder are not currently showing live on the site.
I was hoping I could build out the theme and then deactivate builder leaving the new theme active. Do I have to build the theme entirely on one website and then export it over? It appeared to be working as I expected and then out of nowhere it's now no longer making the updates.
I've also noticed if I try to add a version number that an oops this failed error is popping up, not sure if this is linked. I will give support access now and have already upped the wp memory to 1024mb. Many thanks in advance.