I'm having the exact same problem after updating to v81 and have spent many, many hours searching for a solution, unfortunately in vain; the problem is still the same. So far, I haven't found a proper solution. I hope Meta resolves the issue as soon as possible with an update patch or something similar!
Hi, yeah there wont be a solution until its fixed. My way around it has been to not turn it off. I leave it in sleep when not in use, just keep it charged. In my case, 15 hours of sleep took about 3% battery so its feasible.
You'll use more power if its running game updates etc.
