Stuck repeatedly syncing one file

Insync is currently in a strange state where it seems to be stuck trying to upload a single, 1KB file. As soon as it uploads it (or tries to), it goes back to “Scanning for changes” - then about 20 seconds later, it tries the same file again. The file is NOT present in my Google Drive.

Although there’s not much to see, here’s a video showing Insync attempting the file, and the Explorer window in the background showing that it is unsynced: https://drive.google.com/open?id=179xtD-l-QkLNWtrlPuDLp27FoEZ9bAs6

Coincidentally, after I uploaded that video to my Drive and Insync pulled it down, it has now changed to “No ongoing transfers” and has a green tick in the system tray - but it is STILL trying to upload that file once every 20 seconds, and my Google Drive folder STILL shows up as unsynced in Explorer. Any idea what’s going on?