As shown in the picures, tonly show the the sidebar seems to start at the lowest score and not the ones that are "leading" when hitting the player limit of the sidebar!
So when I have atleast a score of 1, my name will dissapear from the sidebar because the other player's score are lower than me and i would be higher than the sidebar's maximum slots.
When I have a score of 0 again, my name will be sorted in lower causing it to show up again (just see the pics)
To solve this, i would recommend a decreasing instead of an increaing order or even something like /scoreboard objectives setDisplay sidebar walk increasing/decreasing
Hope you fix this for us mapmakers