Note wouldn't sync changes

Running Joplin 1.3.18 on Windows. I've had sync working pretty well with Dropbox for a while now. I've made lots of changes, and sync was working well.

Today I made changes to a note, but Joplin didn't sync them. I tried multiple triggers of manual sync... the note simply wasn't synced. Then, I made changes to the note again, and everything synced over just fine.

To clarify... I can't be 100% sure the problem didn't occur on my Android.

Any ideas how to proceed, and whether I should be concerned about this being a recurring problem?