Did you bleed your injector of air bubbles if you poured plastic into it instead of sucking plastic into the injector? Might check your injector o ring. Also when I’m injecting a body onto a tail I shoot it hot. Like 375 and hold pressure. Too cool and not a good bond. I hear some people put their tails in the molds and then put on the molds on a hot plate to warm them up so that the tail plastic is heated.