I had that once. For some length of time, although not the full half hour suffered by the OP. The unpleasant proximity, leaning over, handling the back of my seat were also accompanied by the sense of a deterioration in air quality at the level of my face. Thank heavens not the worst, but not helpful.

Thanks to all posters. I'll be implementing some of your suggestions here the next time. I particularly like the posts about using the call button so the FA might have less ease in dismissing it.