variable timeout between the slides doesnt work when img is the background image of li element

[SamLad2015]

I am using the following html

test2.txt

save and run the above file as html

I am expecting a delay of 8 second between the second and third slide but the delay is the same as whats between the 1st and 2nd slide. Do you know why this would happen or it is a bug?

Thanks