Can’t delete files from an old project because MacOS says they’re “in use”

I’ve had this odd situation where my bin fills with files as soon as my external hard drive with all my old project is inserted. Every time I try to empty the bin, it says some of the files are “in use” and therefore can’t be deleted, however Logic isn’t open and even the project itself has been deleted. Anyone know a workaround for this, there’s around 30gb of leftover audio files lingering in the bin.