Hey Marc, Yes I have noticed this a couple of times too, I notice it happens when you are not touching RB for a little bit of time. If I wait like 3-4 minutes of not doing anything on rb, for instance, playing a song on a cdj, then go and sort to BPM, it does not sort the first time I click it, I have to do it twice.
It was very easily reproducible and i got it on video for the engineers to see exactly what you are talking about.
I hope this is the issue you mean, check this out: https://www.youtube.com/watch?v=GR178_D8shw
you can see no matter what i choose it all not sort until I choose the same category twice, then it sorts fine