Realized after re-reading my lengthy post that other related elements may not be the case with the original authors issues. If a device lives on AC power for most of its life the 80% does wonders to ensure the battery is in the happiest state for longevity. It is so strange that other manufacturers do not incorporate this in their firmware offerings as it really does extend the battery life. Lots of times their warranty is only for 1 year, maybe three if it is extended, and the warranty replacement rate is pretty low overall.
Not being the case here does help identify that it really is likely related to an EC/BIOS issue and subsequent kernel panic from the OS. There is a BIOS bug tracker on the Framework Github 
page where this datapoint might help the engineering team narrow down what is going on.
Frequently, users have posted about system shutdowns and reboots and more often than not a low voltage/battery is involved. 
There is definitely a trend of the newest laptops that have not held up as well as laptops made years ago. 
Lots of newer electronics are just not as robust since profitability is the name of the game for many businesses so what may have started as a “square” product has had so many corners cut, everything is rounded out! 