Before you shoot your next roll, have a look at the roll you just shot. Are the rest of the frames evenly spaced? How much extra film is there at the "tail" of the roll; that is, at the end, after the last exposure? If the spacing is good, with no overlaps, with even rebate areas between the frames, then you aren't suffering any film slippage. If you are, then the transport mechanism may have to be serviced.
I was recently gifted a very nice Mamiya C33 camera, which is similar in concept to the camera you have. When I shot my first test roll, I found that there wasn't enough rebate area at the "head" (beginning) of the film, and too much at the tail. I measured both of the rebate areas, and compared them. The result is that, with my favorite film (HP5+), I advance the arrow on the backing paper about 3/16" or 5mm, past the index mark on my camera. So far, so good.
I have yet to check with a roll of FP4+, but as both are Ilford products, I am confident that it will "line up" in the same manner as HP5+. If you test with one manufacturer's film, another manufacturer's film may not line up exactly the same; I have had that experience in the past when loading my Rolleicord.