In order to determine when surface-by-surface bundles are non-positively curved, Llosa Isenrich and Py [Math. Ann. 380 (2021), pp. 449–485] give a necessary condition: given a surface-by-surface group
G
G
with infinite monodromy, if
G
G
is CAT(0) then the monodromy representation is injective. We extend this to a more general result: Let
G
G
be a group with a normal surface subgroup
R
R
. Assume
G
/
R
G/R
satisfies the property that for every infinite normal subgroup
Λ
\Lambda
of
G
/
R
G/R
, there is an infinite finitely generated subgroup
Λ
0
>
Λ
\Lambda _0>\Lambda
so that the centralizer
C
G
/
R
(
Λ
0
)
C_{G/R}(\Lambda _0)
is finite. We then prove that if
G
G
is CAT(0) with infinite monodromy, then the monodromy representation has a finite kernel. This applies in particular if
G
/
R
G/R
is acylindrically hyperbolic.