Clean install 1809 on a Toshiba Sattelite radius 14 L109 wont work olso.
I have stop windows update and stay on the 1803 no problems at all
Microsoft still sends updates for 1803. If you have targeted update (settings), MS will not repeat 1809 update if failed (but you have to revert changes made during installation). Upgrading through Windows Update Assistant worked for me (but I updated Lenovo BIOS and switched off virtualisation befor it).