Kirk,
Thank you for your continued efforts to look into this. I attach the PMDebug log file, but I suspect it will not tell you anything useful - it appears only to record debugging being switched off and on (before doing this today, it was already switched on).
I tried the menu removal command, and removal worked from that, according to the collection. I will rerun a full sync and let you know if they return on a new sync. [Update: the new full sync returns no offline images. It looks as if the menu command works even if the right click contextual menu is greyed out]
Replying to your previous post questions, I cannot think of anything that may have happened between the phantom files having been originally catalogued and now. The I: drive is a 6 TB Seagate Barracuda SATA drive, it was the last new internal drive I installed a little under 3 years ago. It contains image folders, 3 folders of Macrium daily incremental backup files and an old Capture One catalogue that I have not accessed for about 9 months and which does not contain the originals of the phantom files. It does not store any system temporary or cache files. It remains my current disk for storing new images as and when they are added. I have not reorganised the images on this drive beyond the addition of new images as they have been taken, adding derivative Photoshop images made from the RAW files and deletions from occasional culling. I often tweak keywords which will mean that the .xmp sidecar files will have often changed and also the colour labels, which I amend to group panorama files visually and to reflect what I have done with exported images. I cannot think of any external operations that might have deleted the root level .pmshare file. I have not re-organised or re-allocated the drive letter for this drive since it was originally installed. Sorry that this is not very helpful, but as far as my use of it is concerned, it is only for image storage and backups.
Graham