It's a timing issue, but not necessarily the hook itself. I've had needles off sync because of dirt behind the needle clamp, when I took it appart I ended up scraping out a lot of dust and grime from the groove in the needlebar. It took me two weeks to discover it; all cleaned and reassebled the needle was just in the right place. All kinds of issues cause these things.
As the upper thread gets picked up for a ride around the bobbin case, it picks up the bobbin thread and they interlock and tighten up by the upper tensioner. The bobbin tension is there mostly to guide the bobbin thread and firm it slighly up; all the action is initiated by the hook and upper thread. In other words; I don't think the take up lever should affect the upper thread at this point; it might be just tension (non at all?, is presser bar lever up?) If I'm thinking right the takeup lever brings around just enugh thread from the top spool for the next stitch. And the tightening up happens as a combined action of the thread interlocking, needle movement and just the right tension.
Last edited by Mickey2; 09-15-2016 at 02:35 AM.