Path Not Filling All of Shape and Filling Outside of Shape

Thank you for sharing, Clara.

It is valuable for helpers to see whether our assumptions are right, and to see whether suggested ways can be expressed better.

In this case, there were the assumed non closed paths, and I can ponder over how to better express the suggestion of closing the path(s) (possibly) by joining, as you actually did.

For my part I hope you will share your findings, Clara.

Nevermind, I figured it out. Thanks anyways 

Can you show such a path when it is selected?

(use the insert photos button)

Clara,

What you describe could be the appearance of a non closed path (set); like what you see if you create an open filled path with a (maybe soft/rounded) zig zag shape.

If that is the case, the solution is to simply close the/each ailing path, possibly by joining multiple open paths that ought to be one closed path.