I never heard of running a gennie specifically for an electric heater, about as inefficient conversion setup possible. As for the meltdown, I think more likely the electric regulation system of your generator went out of spec. But of course different heater models/manufacturers have different quality, and in fact within one brand name I have seen huge differences between different models, or over time. And a lot of outsourcing/rebranding going on. For example the classic "Pelonis ceramic disk" heater from 20 years ago goes for a lot on eBay, because they are famous for efficient heat output and last forever, people even rebuild them. But the new ones sold at Wallies, not so much. I stand by the general relative safety of electric over ventless propane usage, you do need to know what you're doing with the latter, and no matter what, the inherent risk is much higher. But in a PUP at least you are likely getting some fresh air intake even if you forget to open one.