Same problem too

i tried this @HuskyDynamic01, but it still wont disconnect!

The detacher has two connection points, one on the top (the thinner end) and one on the bottom (the thicker end). When triggered with an activation group or other input, the top connection point is the one that separates, so the detacher itself stays with whatever is attached to the bottom part.

Make sure that the parts you're trying to detach are only connected to the detacher (and any other parts being detached), and not to any other part of the main fuselage. If even one part is connected somewhere else on the plane, it won't be detached because there will still be a connection point.