Illegal image when attempting to update VMG1312-B10D firmware

VMG1312_B10D

I have a Zyxel VMG1312-B10D on firmware version V5.13(AAXA.5)C0 (released July 2017). 
My ISP is Zen internet and they do not require an ISP specific firmware version. 
I am trying to update the firmware but keep encountering an error 'illegal image' followed by the router rebooting. I am using the .bin file as instructed. 
There are two new versions of the firmware available...5.13(AAXA.7)C0 (released Dec 2017) and 5.13(AAXA.8)C0 (released Oct 2018). I have tried installing both but neither will work. 

I have tried in Chrome and Internet Explorer...I am running on Windows 10. 

Any suggestions of what I should try next? 

#CPE_Nov_2018

AAAAL

Hi VMG1312_B10D,

Try to clear the browser cache to see if the firmware upload process can succeed.