This afternoon as I picked up the phone which had been lying idly, it showed a notification from system downloader which said something like:
<Untitled>
Download Error
In Files -> Downloads, there was an unnamed file of type "file", the info of which only said "queued for download". I deleted that file after several unsuccessful attempts of extracting any more info.
Neither RethinkDNS nor the system logs seemed to have entries for that time (at least meaningful ones, except maybe for ntfy app in RethinkDNS?).
Auditing the device shows it's untampered with (yay!).
Unfortunately due to a reboot in between the logs now seem lost.
What could cause this, and how would I properly investigate if it occurs next time?