I have not been able to repeat the behavior you are reporting so I need additional information.
The best way to give me all of the details is to save a g-code file with the "Suppress Comments" option turned off in the "General Settings" window. Also include the image you are using as an input.
If you send me the g-code file and the image I can run F-Engrave with your exact settings and input. Then I can see the problem.
You can send the files to the e-mail address in the F-Engrave help menu.