This has happened on three separate windows machines, each with an independent installation of Ardour.
What happens is when I record a stereo track in Ardour is that while recording it shows both channels as it records. However: when I click stop to end the recording, the waveform of one channel disappears. It is always the channel on top that disappears, and after resizing the track vertically it shows the second waveform again. Not a hugely pressing issue, but one that has cost me a bit of time now and I’d imagine others as well. Let me know if you need any further info.