lws380, a burr possibility had occurred to me, but I don't think there is one, as brown and white are going through the machine just fine.
George, I am using 277 on top and in the bobbin. For holsters and belts, should I be using 207 in the bobbin? I am very new to sewing with a machine.
Also, I don't know what the needle size numbers you referenced mean. The packages I have show 23, 24 and 25 as sizes. I am using 25, the largest.
What is a lube pot?