CAS : strange error on simplify

[primer]

Hello,
in CAS setting, please select "USE i", "complex" and "Maximum simplification"
now type the following (-sq(2+sq(2))+i*sq(2-sq(2)))^2
ok, now press ENTER
and I got this message :"Warning! Algebraic extension not implemented yet for poly [-1,0,8,-8,2] " displayed 4 times on the screen.
very strange for a so simple expression

Please note we don't have message if we choose "minimun" as "simplify in CAS setting !
Best Regards.