Not sure if this will be helpful or not but I just got my 6s+ yesterday and was messing with the default Live Photos and came to the same conclusion aboutt it not worklung for the wallpaper. For those of u trying to view them on the lock screen or photos u've taken, I seem to be having the same trouble. the photos only respond to my touch about ten percent of the time. i have to press rather firmly to get it to start and while still holding my finger down, the photo will sometimes stop on its on halfway thru its motion clip. It works perfectly for my girlfriend however so my thinking since my hands are somewhat rough and calloused maybe it's a sensitivity issue.