Hi Terence
I too am having a problem with a corrupt library
I only noticed when updating to 'Photos' a couple of days ago, so restored my system to a couple of weeks ago to get rid of 'Photos' but now there is still a lot of greyed out invisible pictures that I can't access/missing in 'iPhoto', so the 'iPhoto' library must have become corrupt some time ago
I've tried the 4 different first aid options in iPhoto and none have worked. I've even made sure all the permissions are correct, moved the library to an external drive, etc, and still the same pictures are missing in iPhoto.
Searching through the numerous posts on these matters I see yourself and someone called Old Toad have both been very helpful to the community over the years with your suggestions, and both bring up iPhoto Library Manager a lot. It appears this may be my last resort, I assume you must have had some success with the application in the past. Do you use the paid version or free trial? Do you know what limitations the free trial has when trying to rebuild a library?
Alternatively have you ever tried or would recommend creating an entirely new library in 'Photos' or 'iPhoto' and then just importing the Masters and Preview folders from the 'show package contents' in the previous iPhoto library?
Many thanks in advance