Do the stems line up with the holes under the space bar. If you flip it upside down and put it beside it, it all lines up right?
If it is the case the that stabiliser is just not staying in the hole, you can fix it with a little thin plastic over the stem to take up the gap.
From your video, half the stabilier the right side, is seated correctly, but the left side seems to not be attached at all.
EDIT: Looks nice though.
Get some pics of the under side of the space bar sat next to the stabs, and/or the new spacebar under side next to the old one.
As for the gap cling film/saran wrap work good.