Could be that the switch is failing, but I think I would pull the switch from the wall and check the wires attached to it.
More likely they have come loose.
Oops, on edit I re-read your post and those lights are not on the same switch, but they might be tied together so it would be a good idea to check the wires anyway.
Also I would check the junction box either below the slide and/or inside the slide on the lower wall.
Peace
Dave