Thanks for sending the Droplet for testing. From what I could tell, everything is working on my side. As you mention, this behavior appears to be intermittent (sometimes works, sometimes not). This suggests there is something going on beyond the droplet, LR, or PS. Most likely, it has something to do with the files you are trying to edit themselves. Are you working with all files from a single camera, or at least a single file type? If not, try testing with all the files in the same format, from the same camera and see if you run into more success.
If the files are all essentially the same, try running LR, the droplet, and Photoshop in this workflow from a new user account, in a new Lightrom catalog.
Thanks for taking a look. Yes. I'm working with raw files (.CR2). I'm working with files from two different cameras but they're both 5DMIIs and all the files are raw. The problem has happened across multiple catalogs. I actually create a new catalog for each event/session/job, and I've had the same problem while working in different catalogs. I'll continue to play around with it.
Let me just ask...did you do a "select all" of all the images (or at least multiple images) in the catalog, and edit in an external editor?
Again, thanks. I'll continue to play with it. I really appreciate you looking into it.
If this happens across multiple catalogs, but it used to work universally, then the next thing to look at is your user account. Try running from a new user account and see if the behavior persists.
And as a note, I first tested with just a single file to verify things were working correctly. After that succeeded, I didn't do a select all, but just a small group, like 5 or 6. The process worked the same, all files were processed.