I've worked on multiple 5s & SE models, and i havent found any difference between them as the screens are completely interchangeable. I have heard however that aftermarket/cheaper screens give problems when not put on their respective phones. As long as you get OEM screens or at least ones from a reputable source, everything should be fine. Sounds like the guy at the store either gave you an aftermarket screen or a bad one in general. Try putting it on another 5s & see if the problems persist