Can confirm, both. KaiOS has tons of bugs and vendors usually ship old buggy versions. But the hardware itself often dies or has flaws, because it's the cheapest phone you can make with modern features (bluetooth, wifi, 4G LTE, a multitasking OS that can "run apps", etc).

The problems I see with KaiOS are 1) lack of aggressive development to fix bugs/features, 2) lack of vendors upgrading the OS on new handsets, 3) lack of vendors upgrading the hardware to run newer versions of the OS. And the market doesn't really care (or have a choice), they just need the cheapest phone possible that can check the weather forecast or email.

Until both developers and vendors give a crap about building efficient technology, they will continue to churn out bloated, buggy software on cheap hardware. Even Palm Pilot was more advanced than the crap churned out today.