I saw similar problem few times already and the main reason is the layout 
The Collection list Wrapper has no width, then the Collection list set to width: 100% and display: flex.
When filtering happens and items getting “removed” from the container (Collection list) it shrinks automatically because 100% of nothing (remember, no width set on its parent 
) is … nothing 
.
So if you will make Collection List wrapper to width: 100% it will keep all containers in place and animations will not look so weird:
Hope it clears your doubts
Cheers,
Anna