I think one of the ways they save money is using cheap wiring, so it gets hotter than it should. Also, no waterproofing - which is why I no longer have my Xiaomi.
My previous phone was a Xiaomi and I never managed to unlock it. It would fail to unlock and then there would be a random amount of time before you could try it again. After weeks of that I didn’t want to have to set everything up again and just worked at removing all the telemetry and spying.
I just bought the Legendary Edition on Steam for not much at all, cheers