I made iPhone backup on Macbook and then copied the backup folder from the library to Sandisk external SSD. I don't need it any more. I erased it from Macbook and now it is impossible to erase it from the external SSD. While emptying bin it always says "item in use" etc. How to overcome this nonsense and to erase it from the SSD disc ? (it occupies 200 GB). Nothing of it is in use , it is nonsense.