That's exactly what happened to my wife's device. It suddenly wouldn't last more than a few hours... She took it back to the place she bought it from and got a replacement.
The charge five isn't really a Google product. Google were still in the process of buying Fitbit when it was released. And as someone who's owned the charge HR (bad band), the charge 2 (great device, miss it), the charge 3 (died randomly - screen was backlit, device was charged but it would not wake up after an update), the charge 4 (still going strong, use it for work), and the charge 5 (too fragile in my opinion but a nice device), I can't say I'm too surprised. The software update I will admit is google, but Fitbit had problems with device QC and quality long before Google bought them.
You know it's just sad. Fitbit buying Pebble and not using any of that in their watches. Then Google buying Fitbit and not using any of that tech either. Just so much potential being wasted.