ASD5 Standalone wipes source disk

Just started using ASD5. If I try and read an image file from an external hard drive attached to the local machine and accept the default settings the partition info is read from the image and used to replace the partition on the external hard drive instead of the internal disk - resulting in failed to read image after that. The Standalone utility works perfectly when reading an image file from the network and installing on the local disk.

I have repeated this several times with the same result. Never had this problem with ASD4 used in the same way.

Am I missing something here? I would expect ASD to at least give a warning if it was trying to overwrite the disk containing the source file.