I traced an bmp externally using potrace and imported the svg into FontForge. This is the svg:

However, if I run simplify glyph, the glyph will turn into this:

This has massively bloated the file size and converted two straight line sections into one long curve. All options in the "Simplify more..." menu can avoid this issue.

sample svg: cid09487.zip

FontForge 20201107, Windows 10 21H1.