Very old DM gets stuck close to top after being opened but with no new activity

[simfur-ritwed]

I recently went through multiple old DMs which last had any activity over a year ago. After doing so, one became stuck in the 4th-from-top position in my DMs view despite no new messages. None of the other old DMs I opened seem to have shifted position. Said old DM is now making its way down towards the bottom as I send and receive new DMs. This situation has persisted through multiple hard refreshes of the browser.

System: Chrome on MacBook Pro.