Open the front door when the paper is over the 2nd btr and check the image on the transfer belt. If the image on the ibt belt is good then it is probably the 2nd btr. If not then it could be the the roller on the bottom of the ibt assembly. It could also be the way the ibt assy is sitting in relation to the 2nd btr.
Much better pictures. It looks like a failure of 2ND BTR.
It seems to be the fuser module. Take a look at it.