PSD Thumbnails - Anomalous behavior
So, I had this happen this morning: https://i.imgur.com/3PCfdNY.png
That's a single PSD file showing a thumbnail.
What in the heck did I do, and how do I do this again for all of my PSDs?
The properties don't look any different than any other PSDs I have: https://i.imgur.com/IVgwUYJ.png
Why is this one file different?
I saved another file from the same day, replicating the process I went through with the file shown above, no thumbnail.
That one file is a beautiful glorious anomaly.
How do I replicate that 10,000 times?
Edit: I went in and played around with the file some more and now it's broken again, no thumbnail.
So, what did I do originally?