the chip on the cartridge is what tracks your printing and notifies you if youre low or empty. I’ve seen people using arduino to reprogram that chip to allow more printing with a cartridge that isnt quite empty or has been refilled.

I would guess the biggest risk with what you are doing is getting the inside of the printer dirty with toner from toner dust on the outside and messing up the quality of the prints

https://www.lifewire.com/meaning-of-red-light-on-motherboard-5189456#:~:text=A%20red%20light%20on%20your,also%20cause%20a%20red%20light.

maybe this has info that will help you make it go away

try going to the website of your motherboard manufacturer and finding the network drivers specific to the model of your motherboard and install

theres always the chance that the drive was failing and it happened to fail catastrophically after you did your work. or maybe whatever restructuring you did exposed a bad sector that made it not work as it should. what you might do next time is test the drive on a computer running the same os as your customer is before shipping out