I get similar behavior when I've got an edit window open while a track change occurs.
In general there seems to be odd behavior &/or inconsistencies with file selection and the tagging window. Sometimes (but only sometimes) the tagging pane won't update when a new file(s) is selected so that, even though the selected file shows as selected in the view scheme, data entered into the tagging window is applied to the previous selected file. This tends to be frustrating as you need to keep a close eye on what file is showing in the tagging pane. I have a feeling there are a few of my tracks floating around with their neighbors' metadata on board...
I certainly don't know for sure, but these two issues and your issue all feel related.
-JB