Sorted the non startup of YazFi thanks to your suggestion above. The Yazfi client was disabled on the main guest page but not on its gui. If I changed that then yazfi would start up fine and all DHCP settings behave as configured. However, once YazFi was running I then lost access to local IoT things - back to the original problem.
Being somewhat lazy as I don't need Yazfi functionality at this time so have disabled it - postponing the problem!
Being somewhat lazy as I don't need Yazfi functionality at this time so have disabled it - postponing the problem!