Probably not worth fixing, but I thought I’d mention it.
I think what happened is that I clicked on a plane on the Flightaware dump1090 table, which I had sorted by distance, right as the plane was aging off (the 1 minute timer). I realize planes stay in memory for 5 minutes in case they come into view again. What happened in this case was that the information box was displayed, and the plane’s trail was displayed, but the icon was gone (my transparency logic would have made it invisible anyway), but it was not appearing on the table. The info box continued to update until it was 321.4 seconds old. Then the box stopped updating but continued to be visible.
I’m guessing the scenario is difficult to replicate, because I think I had to tap on the plane’s table row at just the right moment. I’m posting this mainly because I find it an interesting anomaly.