Thanks for your help I missed the wall thickness detail, I don't know why that setting changed, all my walls are set to uniform thickness.
p.d.
It wasn't my intention to upload the thread so many times I was having problems with my internet connection and hit submit and refresh a couple of times.
iMac - MacOs Big Sur 11.6.6
Archicad 24 - Latest Build
Archicad 25 - Latest Build