As far as I know, there's been no change here between 12 and 13 but Drag and Drop can be different between 11 and 12. Might you have updated from 11 or older to 13 here?
Also, the storage option specified for the container field can make a difference. Might you have specified "external storage"?
There's a download link to a file int that thread that you can use to inspect the full text that can be extracted from a container field. I recommend downloading this file, doing the drag and drop and then inspecting the text in the file. There's also a more sophisticated calculation field example in this file that extracts the file name from the container field no matter what combination insertion method and storage option is in use for that field.
Note to self: really need to investigate GetContainerAttribute to see what it can or can't do...
I see only versions 12 & 13 on my machine, so I'm certain the upgrade was as described.
Yes, I do have external storage selected on the container field.
I"ll try the files you suggest. The GetContainerAttribute try was the result of a search. LIke I said, I don't know why it would suddenly stop working. That has not been my experience with upgrades.
I'll take a look tonight...thanks for your help.