So far I noticed the following pattern:
Windows works without issues, until an upgrade occurs. Once the upgrade occurs and I'm asked to reboot, I lose Bluetooth keyboard at OC boot picker and I'm forced to use wired Mac keyboard, in order to select the Windows drive (I cannot set it anymore by default in Big Sur). Then I get the dead Windows logo, forcing me to shut down the Mac while holding the power button.
After two reboots into Big Sur, I go back to Windows disk and this time I'm prompted with an Automatic Repair logo. I get several repair options, but I select the one called "Exit and Login to Windows." The usual upgrade percent happens and I'm able to login into Windows.
What I did today different after upgrade was to download the latest Pulse RX 580 drivers and updated the Microsoft drivers that were installed. I extracted the drivers package and in Device Manager I right clicked on Radeon RX 580 and selected to update drivers, then I pointed the installer to the extracted directory.
I did all this because I did not wanted to have all the bloat added, the drivers install took quite a lot of time, at least 10 minutes, while the screen flickered several times.
Now I need to wait until next upgrade and see if the I still experience this issue.
or anyone else, what I need your help with is the /Boot/bootx64.efi clarification on Windows drive.