So since I've had some success in the case where a ghost appears and the "Remove" button under Z-wave details does not work. Now this works only in the case where the device is powered up and you can activate the z-wave pairing sequence on the device.
What I observed is that even tho the device is powered down, the remove button will not remove the device. Well what has worked for me the last several times, was to go to "Add Device"-> "Start Z-wave Exclusion" and perform the particular device's exclusion sequence.
This just worked not 2 minutes ago with my Aeotec 7 repeater. It became a ghost(route box blank) and would not remove using the remove button in Z-wave details, even after many tries. However the very first time I started Z-wave exclusion from the "Add Devices" button, and tapped the repeater's button and instantly the ghost was gone.
If anyone has a ghost I'd be very curious if this method works for you. Obviously if the device is dead or otherwise inoperable this will not work.