This problem something simple I am doing wrong, but when I put on the petal-type lens hood (that came with the lens), it doesn't rotate fully to the proper position. The little arrow under the Sigma name does not align with the dot on the lens, and you can see that the large petals are not aligned vertically (close but not quite).
I am not game to force it, but maybe it should click into the final position. There is no resistance as I slide it around and I get the feeling something should click or tighten to prevent it moving and even coming off if it rotates back far enough.