Totally missalined results

Hi there, I am new on this business and just started a few simple projects to burn on plywood. I have an ORTUR Laser Master 2 equipment and replaced the original laserhead by a 40W PWM laserhead. I design my graphics on Corel Draw, export to dxf files and import into Laserburn what seems to work good. Here I am doing some fine tuning before burning (add or remove some lines, lining up grafics, reorganize layers… etc.) But finally when I burn the project it gets messed up on just some parts of the grafic. What is going wrong ? Somebody can help me ?