fdisk: Can't read secondary GPT header: Invalid argument

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I just replaced a failed (SAS) disc in a RAIDframe RAID with an identical one. 
Everything seems to have worked well, only fdisk utters
	fdisk: Can't read secondary GPT header: Invalid argument
combined with a kernel message
	sd0(ahd0:0:0:0):  Check Condition on CDB: 0x28 00 04 47 e0 e7 00 00 01 00
	    SENSE KEY:  Illegal Request
	   INFO FIELD:  71687372
	     ASC/ASCQ:  Logical Block Address Out of Range
fdisk says
	total sectors: 71819496
of which, in disklabel, I only use 71680000.

I tried to scsictl detach the failed disc, but that gave me something like 
"device busy", so I just swapped.

Why is a GPT fidsk's business?

Would there have been a method of cleanly detaching the old and attaching 
the new disc?