Try cleaning the lens first, don't use rubbing alcohol, it leaves some residue, so parang may naiiwan na lens even after cleaning it. Use lens cleaner liquid or even water. Make sure the support rails are well lubricated, sometimes kung tuyo na nag skip-skip or humihinto at certain areas. Adjust the laser's diode para lumakas ng konti. Adjustments should be done gradually. This should be the last thing you try since you can give the laser an earlier death. Or baka papundi narin yung laser, so maximizing it mite speed up the process.