alright, so i've flashed the latest oreo rom using the steps here: (https://forum.xda-developers.com/t/...e-moto-g5s-plus-sanders.3681018/post-74065631)Hey, man.
Download the firmware for your country.
You'll probably have to do it using ADB Fastboot, since it's hard to find a flashable Stock for Sanders.
Once you've done it, update it to the last firmware available, using the update function within the Stock Oreo ROM.
Then , and only then, you can install a custom recovery (TWRP) and custom ROM.
Hope this helps.
Good luck !
The same situation, I had to return to 4.7.
/* * Your warranty is void. Or vaild, probably? * * I am not responsible for bricked devices, dead SD cards, Ebolation X, * thermonuclear war, or the current economic crisis caused by you following * these directions. YOU are choosing to make these modificiations, and if * you point your finger at me for messing up your device, I will LMAO at you. */