Because the vectors are not closed the free MS 22558 font if you're using it has holes or unclose vectors. 3 d modeling programs are also not very good at text.
I would suggest you make your panel out line and holes and any relief for pcb in the 3d modeling program. Then export the face of your file to a DXF. file and import it into Corel Draw and place your text with your chosen font where you would like it, and save as a corell file then a DXF file for engraving.