Error starting from boot menu

[Petey]

@al3x:
Thanks very much for your suggestion.
Unfortunately, I do not have an image with the error on it. But I have a log of all installations and updates I did since I made this image, so I will repeat these steps and check.

And thanks for the hint to use WizTree. I have it, of course, but never used this function. To check for differences, I use Beyond Compare.