LG Electronics — Unethical Marketing and Looting consumers

I've purchase LG AC dual inverter with 1 year extended warranty. Purchased in 2020. Along with Ac I have also installed V gaurd stabilizer. Company market the product that we dont need a stabilizer for this Ac. After 2 year Ac was not working and called LG customer care and they have send a technician. Technician Checks and says that the PCB is not functioning due to power fluctuations and it cost around 6000. My question is Why the issue is with this AC only whereas other AC is works fine. And why are making defective products which will not work after certain amount of time and PCB doesn't with stand after stabilizer is installed. Everything looks good in the PCB once he changed with other PCB is working. Just simply looting customers money. LG is scamming public with false marketing.