Project on a Bamboo Board randomly burnt to a crisp

I have 4-month-old Omtech 60-Watt laser that has approx. 250 hours on it. This project I have done before with no issues, same project same type of Bamboo Board but this time, it randomly burnt a few areas to a crisp. Any ideas why it would just burn these spots so badly? I have checked the alignment of the mirrors and the main Lens, everything looks OK.