There isn’t any solution except don’t use WinCDEmu. One of the feature request, extreme easy to implement, of my thread “Basiz…we wait you!” was Remove the ISO, not the drive itself
This is the problem, some multi-disk installation search for the same drive but the drive change everytime you mount an ISO. So or you wait for an update ( listen, don’t loose time the author in this section is desaparecidos… ) or change the software.