In the German FAA registered they have the strange habit of re-using registrations.
Take a close look at het 7 pictures attached to D-IETZ. You'll see that 5 of the are of a different type.
Only two of the seven pix are of the CJ2 c/n 525A-0363. The other 5 are of CJ c/n525-0518 and to make it easier for us: with the same owner/operator.
Good luck with this problem.