Since 1.4 the Detpack seems to have minor issues sticking to the AT-ST, you can still attach it to the leg with a really accurate throw, but dropping it on the footpad results in it falling right through it. Sometimes it does this but connects some how so when the Walker walks away it drags the Detpack with it though there is no visible connection. You just see it floating beside it moving in time with the Walker's leg. I presume this is some sort of col mesh issue.