Yes I have replicated this in all 3 major browsers (Chrome, Firefox, Edge). I don't use firefox or edge, so those have no plugins or anything installed.
The issue i see with your video is that you are "scrolling" from May to June. Perhaps this was lost in my long post, but I did mention that scrolling works fine. The unexpected behavior is only found when "clicking" from May to June.
So to reproduce: Open the date picker, mouse click June. If you scroll then you will not see the issue. You can see if the GIF that I am mouse clicking and not scrolling.
Please let me know if you have any more questions regarding the issue. I understand this is a difficult issue to explain but I am trying my best. If needed, perhaps we can setup some sort of remote session where I can demonstrate the issue live.