Downloading Firmware Broke the Device?

[CaliCo]

A few days ago, I was downloading the latest 2.1.1 firmware on my Onyx Nova. It was being charged at the time.

I clicked on download and left the device as is. The download failed a few times. On the last attempt it froze. Then I plugged it into a different charger as advised by Onyx Support. It rebooted fortunately!

But what I noticed is that the battery level was dropping even though its being charged. Just when it was nearing 0%, it alternated between rebooting and displaying the "plug in" symbol.

Now it is frozen at the plug in symbol. I have tried different wall outlets, charges and cables but no response.

I have contacted Goode-reader and Onyx for an RMA.

What is the correct way to download/install the firmware? Was I not meant to plug it in?

Further Information
I read on the device for 7hrs+ daily with approximately 2-3hrs of frontlight usage. Wifi is manually activated for word searches and turn off immediately. Battery life drops to ~40%, yet I read the battery life can last up to a week? Normal for my usage?