I have known a few people with G-B disease, and in those cases unrelated to flu shots - and of varying levels of severity. But the Flu itself can cause G-B as a side effeect, so it makes sense that where the viruses are used in the flu shot, even though killed, a few will slip through the cracks.
I don;t think there is any medical product that has NO side effects.
And sometimes the effects can be very unexpected. For example, I know of a case where someone almost died during a blood transfusion due to a severe allergic reaction. It was eventually traced back to the donor having eaten shellfish, and the recipient was very allergic to shellfish.

So everything is a risk-reward decision. We each make our own decision.