What is the reason for color crosses the border?
Maybe a GPU Preview problem? Try Cmd or Ctrl E to switch to CPU Preview.
I cannot see it in your movie because you are zoomed out.
How about a screenshot like the first one comparing both Previews?
And CPU Preview? This is what a problematic GPU Preview sometimes shows.
Addititional: Please show a screenshot
Move the (clicked, selected) path a little to the side.
Are there perhaps two or more paths directly above each other?
As a beginner I am not familiar enough to gothrough with all above mentioned steps. But by using Shape Builder Tool I got rid of this problem.
Good to hear you solved it. The Shape Builder tool solution looks like you have an open path.
If there is path overlay Shape Builder tool doesn't work?
Some times using Shape Builder tool doesn't delete the path, but path turn into red color as it shows ready to delete. What can be the reason?