Li Keqiang doesn't look happy when Hu touches his shoulder. So maybe it is health issues?
Also in the sky news video at 1:25 you can see Li Zhanshu starting to get up and Wang Huning pulls on his suit to make him sit back down.
Another theory is that he was dozing off which would look bad if he was front in center next to Xi. A purge would of also taken others of the cyl whom were also sitting next to Xi...