"squashfs error failed to read block" at the end of liveUSB shutdown (after ENTER)

I've encountered the errors after some work on Release 20.04.03 LTS booted from liveUSB stick made with Make Startup Disk of Ubuntu 20.04 LTS.

"squashfs error failed to read block ... -5"

Seemingly never ending at the end of liveUSB shutdown (after ENTER).

I've tried google search but found only related install problems. Granted errors at shutdown are not critical as long as system boots and works before shutdown, still could errors be some warning? Squashfs AFAIK need to be unpacked at boot, what is its role during shutdown?

After that I booted again with self-checking (Checking disks: no errors found message) was done (not skipped) at boot time (then USB stick physically is Ok, isn't it?) with default options and immediately initiated shutdown: the system turned off after ENTER w/out above problems.

If you got the 'Please remove the installation medium, then reboot.' (the message varies on release & asks you to hit enter on some releases; I've taken this from 21.10) your media was unmounted meaning SQUASHFS errors are all you can get in attempts to read the media, on most boxes the box turns off too quickly that people don't get to read the messages - but it is readable on some (and very readable on boxes that don't turn off)

If you got the message 'remove media/hit enter' I'd suggest ignoring the messages, turn the box off (or reset) & quickly eject media & it should boot normally. Once media is removed; if it boots you're all good.