Welcome to the forum!
We might have some members who have used Fontforge before, who could answer that without seeing the SVG file. For myself, I would need to see the SVG file, to investigate.
I mean, it looks like that B is not made as a single solid object. It seems to be quite oddly made, but I can't tell for sure.
Did you make the B yourself? Or was it downloaded or imported from somewhere else?
Would you please share the SVG file?