adobe illustrator - Cleaning up messy corner lines?

I'm kind of new to this stack exchange thing so please bear with me!

Anyway, I'm trying make a ribbon on Illustrator.

Upon making this ribbon from basic shapes and combining them with the Shape builder tool, I end up getting these really messy/jagged corners, and I have no idea what to do and how to fix it...

Any tips/advice/tricks on fixing this would be hugely appreciated! :)

(I'm alright with using Illustrator so feel free to throw complicated lingo at me!)

Also, just in case you wanted to the know the shapes that make up this ribbon...

Thanks again!

Answer

There is another solution: Change the stroke corners to rounded

Square:

Rounded:

Of course, that is assuming you are ok with actually having a rounded corner there as opposed to completely square.