Further info on Brother P1500 thread issues
 

I came across a video on YouTube done by Man Sewing, Rob Appell. The title of the video is FMQ Quilt Compass Quick Tip. Very helpful in explaining why stitches get skipped and why thread shreds and breaks. It turns out as many of us suspected, that depending on if it is a drop in bobbin, front or side load, if the quilt sandwich is moved in certain directions, it can pull the needle away from the hook just enough to cause a problem. He uses a diagram of North, South, East, West. It is very short and I think if you are interested in the video, just searching for it on YouTube you should be able to find it.

I've only tried FMQ once, but this does sound interesting. Thanks for the information.