Try filling in the shapes in this project I made:
fillb9-28-2020_8-01-54PM.wick (3.5 KB)
Result:
In 3 pics, this is what happened and how to solve it:
Yeah but I don’t think the fill bucket should be that way. I thought it rendered the canvas and did a bitmap fill and used potrace on the fill area to make it into a path. So the fill bucket wouldn’t “leak” through the lines. But I don’t think they are anymore because of the “leaking.”
Hey @pumpkinhead,
Thank you for sending this our way. We have attempted to update the fill bucket to not use potrace as it was crashing some user’s computers, or taking anywhere from 10 to 20 seconds to fill simple shapes 
It looks like our new approach still has some hidden bugs that we will need to hotfix throughout the week. It attempts to find a path that connects all edges but, alas, is acting strangely.
I’ll most likely revert this today, and see what the best option is moving forward.
I know that when I would draw with lines or individual objects in Adobe animate, there was a way to break them apart to create one shape. That command, Break apart (cmmd + b) is not working in the wick editor. But looking at the settings, it appears like it should be an option. idk.