Yep, it was a bad wiring connection. I've got longer rails on the Y axis (1 meter) and extended cabling, but some part of the connection is bad. This was a smaller piece, I did a direct wire from the board to the laser and it worked perfectly.
Thanks all for the help! Time to get out the soldering iron again...
Attached is an image of this evening's burn. 8"x12" slate, feed rate of 1700. Took just under 4 hours burn time!