I was experiencing the exact same issue and tried the solution above which appears to have worked, at least for now.
There are some additional data points related to model / OS version etc. and my history related to this issue which may be worth mentioning;
* Model Name: iPad mini 4
* Capacity: 128 GB
* Model Number: MK9N2LL/A
* iOS version: 14.3 (18C66)
The crashes began after updating to version 14 of the OS earlier in 2020, although I can’t say how long after, (it may have been after a sub-version release). Initially the crashing was intermittent which led me to believe that it was application related but eventually it became clear that it was the OS. The symptoms didn’t include the battery issue above initially. When the battery issue began I ran a backup and restore, which didn’t solve anything. I then did a factory reset and restore which appeared to work for a couple of months. I began having the problem again a few days ago (it’s now Jan 12, 2021) which brought me to this page.
2 thoughts - 1) Why does this solution work? I mean, if it solves the problem that’s great but I’d still like to know wtf is going on in my device so I can possibly prevent a recurrence or at least protect myself from data loss or security related concerns. 2) I agree with Jake’s comment above. This is clearly a software or firmware issue, and as such, Apple needs to address it.