What is the best glue(for glue guns) to apply individuals?

I've been using Mega keratin sticks but a few of my customers have had more shedding than I would consider normal... Also, a couple have slipped down from where they were put in... I know I was good at applying the glue all over the ends of the hair and attaching it while it was still hot so I don't know what I am doing wrong...
Is it the glue? Is it me?

I'm very big on customer satisfaction so I want to fix this asap. I'm also the one who posted previously about getting information about shrinkies and microlinks... This will not happen with those too will it?

Please help,
Kristin