bottom thread comes up to top on FMQ...advice?

[coffeebreak]

I am trying to FMQ meander stitch a quilt....top is pieced 100% cotton and thin 80/20 batting and the back is 100% polyester fleece. I have done this in the past with no problem, but... now a problem.
As I test my stitching and movements and all on a sandwich of cotton/batting/cotton...my stitches are perfect. However, if I do the same with the actual quilt..the bottom thread comes up. I am using 100% poly Connecting Thread thread. Light blue on top, red on bottom. In the past, again....if have not had the problem of the bottom (red) coming to the top. And I don't have that problem on the practice sandwich. But on the quilt..red thread comes up to the top. I have fiddle with tension and speed... but nothing helps. Seems the issue is with the fleece as no red comes up with all cotton fabrics.
Any ideas what to do to make the red thread stay on the bottom and not come up with the top thread...apparently when using fleece on the back?