Hello, I tried slow motion recording in two stores. Of the three 6s plus I tried, all of them stopped doing slow motion recording after the 15th second. I asked a sales in the Apple Store. He could not explain. He asked another sales. That person said that all demo iPhone 6s plus has a limitation of 15s of slow motion recording. The ones consumers get has not such limitation. Is this really true? How long can we record in 4k and in slow motion? Thanks.