I have a Janome Horizon 8200 question/problem. My machine is one year old. I am walking foot quilting on a white background. Every 2 to 6 inches, a needle hole will be black. I’ve thouroughly cleaned the bobbin casing. I’ve changed needles twice. I’ve changed thread. Any suggestions!

I have an Elna Excellence 720 and like it although I mostly do walking foot quilting. I can't seem to get the tension right with FMQ, so I take things that I think need swirls to be long armed. But I love the larger harp space and the smooth, easy way it sews. I can't seem to thread the machine using the threader so I generally put a piece of white paper behind the needle. This feature is definitely not great. I miss my old Viking Rose which had a white strip on the shank behind the needle, making threading easy.