Example: Select more than 1 photo from from grid view in LR (make sure each photo has a caption associated with it); then go to File < email photos and fill out the form making sure to check off the box "Include caption metadata...." and "send". I use 4 photos as an example....
The result: Photos 1-4 have captions reversed and associated with captions for photos 4-1 !!!! How bizarre is that?
This bug # LRD-4199829 has been present since at least LR Classic CC version 7.1!!
After hours on the phone (5 calls) with multiple folks I finally got an honest answer regarding the history of the problem. Of course, the case numbers mentioned on the "Form" Adobe sends the customer at the end of a help session, all expire in 5 days unless you keep calling tech support. No wonder Adobe never fixes the problem. This is pure negligence on Adobe's part it would seem. Imagine if you have a contract where you need to send scores of photos with captions that identify people in multiple photos for the appropriate titles and or artwork but you can't do it with a mass e-mail send....send one at a time? Really? Adobe you are the problem here and it appears this bug has been know to you for a long time....please fix it now.