Haven’t used FCarve either, but @Hentsch has likely nailed the problem.
I would try cleaning up the image.
@Sharpsburg_Woodworke has a description and videos showing a straightforward method to trace images here that will hopefully fix your issue.
@mrgnstrn: As a side note, I have Arrow of Light plaques on my to-do list by early March. If you do solve this issue, any chance I could trouble you to post the cleaned image ? TIA