Seemingly same issue here. New MacBook Pro (16-inch, 2019) Retina, running Big Sur 11.4. Samsung 840 EVO plugged into a right-sided USB-3 port via Apple's pricey USB-C to HDMI and USB adapter (Samsung Smart Monitor connected to HDMI). I had forgotten to plug in the power adapter, and noticed a low battery warning (not low enough to cause the MBP to hibernate), so I plugged in the Apple USB-C charger supplied with the MBP into a left-sided USB-C port. Retina screen and external monitor go dead. Finally after about a minute the MBP wakes up and syncs with the external monitor after several failed attempts. Even though the USB-3/HDMI adapter was never unplugged, I got "DISK NOT EJECTED PROPERLY"... This is a SERIOUS ISSUE, as it can brick an expensive SSD. Very disconcerting that Apple has not fixed an issue that has been there for FOUR YEARS.

I encountered this issue soon after turning on FileVault on a 2019 MacBook Pro with the T2 security chip. Things seemed to be running smoothly until I had a WindowServer crash during a Skype session. On rebooting, my password was accepted at login, and in various other places, but not to unlock Safari passwords or change Touch ID settings, and when I tried to reinstall Ventura from Internet Recovery Mode, I could not get started by unlocking the boot volume with any of the user passwords. I could not repair permissions from Recovery mode either, because a password was required to unlock the Data volume, and neither my login password (nor any of the login passwords on the other accounts) were accepted. The fix was to reset the SMC functions in the T2 security chip (the first step Apple recommends trying BEFORE resetting the entire SMC) by shutting down the MacBook Pro, then pressing and holding the power button (ignore the start chime after first depressing the button) for 10 seconds, then releasing it, and waiting a few seconds before briefly depressing it again to turn on the Mac. Apple Diagnostics found no issues, nor did Disk Utility after I ran it from Internet Recovery Mode. The T2 security chip SMC reset seems to have fixed all of the aforementioned issues for me. (It was not necessary to do the fully SMC reset with Control-Option-Shift + Power button).