Hi Dundi,
I am not familiar with this specific printer. But long sorry short is when you are printing two sided on mesh, or even on one sided mesh if it does not have a liner, an ink catch is needed. I am a bit surprised that the ink catch would block then sensors. Although HP has done some odd things in the past.
One way to do two sided registration is when you begin, on the first side, after you have taped the leader to the take up roller and it is under tension. Mark the starting position on both left and right sides of the roll material by using a small cut into the material edge. May be a quarter inch or so. It is very important that you do this at a spot on the machine where you do not forget the position of the material. Once the print is finished you rewind the material all the way back out. Flip the roll, feed in the material, line up the cuts to the same exact point where you made them previously. Provided the material stayed straight while printing and you set the margins the same for both sides, you should be in good shape.
That should get you on track.
Good luck,
SK
