Ah, I was ignoring this error putting the tracker in a try catch block. I finally decided to look into it this week. Found a solution and came here to put in a bug report and found that you beet me to the punch :) Anyways I'm curious if -2 is the proper solution. for myself I was changing the check for tl.y to be on the rows rather than the columns. if(tl.y>=im_grey.cols)tl.y=im_grey.rows-1 to if(tl.y>=im_grey.rows)tl.y=im_grey.rows-1 This fix makes sense to me. My rows and columns are different...