Thumbnails

Iphoto version 9.6.1

OSX 10.11.4

Duplicate photo fixer Version 1.8 (1.8.1)

Some of the thumbnails will not open full size. !is shown.

I have used library manager which i resulted in only half of the 5000 phots being available in the new library. I am not able to date this against the inability to open thumbnails. I have read a number of items re this matter however none of the options have resolved my problem.

Please assist