daverelax, Stop charging or powering up your Xbox One S until the liquid damage is addressed correctly, as you could be shorting out components inside the Xbox. You really should take care of the corrosion that is happening inside the device from the pee/water damage as that could be your problem. A tear down link for your device Link #1, disassembly guide will enable you to get inside the Xbox One S to remove the damage/corrosion caused by the liquid. Use the 2nd link as a guide/instruction on how to clean/repair the device from liquid damage. After this you will be able to power on the Xbox One S and see if further damage has to be addressed. Good luck.
I hope this helped you out, if so let me know by pressing the helpful button.
[guide|65572]
[[Electronics Water Damage]]