If your sewing machine doesn't sound right...
Keep taking it apart until you find the problem! I am busily working on my Judy Niemeyer quilt and it was time for the "every 3 bobbin fulls" clean and oil. So I take out the hook assembly, clean all the lint out, oil rewind 3 more bobbins and put her all back together again. I go to bring up my bobbin thread and darn, I must have put the hook back in wrong because I broke the needle. Luckily I always do the bobbin thread slow and easy so when the needle went down it didn't hit anything with enough force to throw the machine out of timing.
I take everything apart but couldn't find the tip of the needle. Hmmm. Oh well maybe it fell down under. Still can't find it. Put everything back together, correctly this time, put in a new needle and she sews fine but oh my what a horrible noise she is making. My Bernina usually is very quiet. I took her apart 4 more times, testing each time at what stage did the horrible noise start. It was as soon as I put the hook assembly back in. Tried changing needles too. Finally on the 4th try... I don't know where it was lodged but that needle tip finally came out from wherever it was hiding. The culpret! DH was going to suggest a magnet right when I found it. I wouldn't have thought of that!.
Once I found that broken tip I put her all back togther and she is purring like a kitten again. Phew. So don't let that clacky, clunky noise go, even if the machine is sewing fine. A new noise definitely means something is wrong. Keep looking until you find it or get your baby to the Dr. Because if I had kept sewing I guarantee I would have done some expensive damage to the machine.