Really need to see the model and specific example of what edges you are trying to detach to be able to provide help. Sorry about that. Trying to split the edge along the UV unwrap. Sometimes it works, most times it doesnt. I dont know why. This particular horn does not want to split along the edge. If I detach it, i'll see the normal actually split or look like its split. However If I click a face or soft select nearby to see if its actually split, its not. Im completely lost. It seems like I can only truly split an edge if its a loop like a sphere but if its an edge of a square, I cant. Below I selected the edges along the uv unwrap and edit mesh > detach. Still connected. Normal seems split.