I’ve seen lots of these failing in forums, sometimes due bad flash, others by CPU balls failing.
The flash on my $800 Sony 55W808C failed two years ago, after just 5 years, and it seems a very common issue on smart TVs.
I replaced the flash, wasn't able to find a working dump, but somehow It worked with the extracted data from the old chip, although the system partion couldn't be read beyond 75%.
Lost some certificates, causing Chromecast, Netflix and so on to stop working.
Bought a Chromecast with Google TV, disconnected the Smart TV from internet, and that was the best decision, let a $50 device do the hard work, if it fails just buy a new one!