Hello, I am very happy with this sewing machine. I still have three questions. 1. after sewing for an hour, oil dripped down. Today again, I sew a lot of white fabric and notice afterwards that there are yellow spots everywhere. With this I can dispose of all the work as I will not get the oil stains out. WHAT can I do to stop this happening? 2. I have used the original spools. Whenever there is still 1/4 thread on it, it no longer sews nicely, this although I have not changed the fabric. Why? 3) I notice that the bobbin is shaken up and down, back and forth in its place. Is this normal? Thank you for more information. Greetings