So the real problem is grub.cfg contains lines that look like this:
search --no-floppy --fs-uuid --set=root
d847c628-aa10-4bef-92b6-72ebacc07d7b
The probe tries to activate builtin protected-mode drivers, and the
drivers "work", so the probe finds two paths to the disk. Both of them
are wrong. In fact this error would be harmless, except for grub will
later write to the disk (the grub environment block). This desyncs the
RAID array.
The correct solution is to explicitly specify the driver is to be used.
