I watched your video you posted and followed it exactly and it still was doing it for me. I even reinstalled the plane thinking that would help. This last time is was KLAS and runway 01L.
The only thing I can think of is I used the Altimeter from the sky pad which said 2983 I out that in the MCDU as 29.83. And after I was approaching ATC gave me 29.77 so I switched it to that and it went haywire.