Mina--as a tech I called once said--if you are at the machine--step back a few feet, take 5 deep breaths, get a drink of water and then we'll talk! So frustrating when you have problems.
Sounds like the needle is in correct if you've checked with magnet and know that scarf is facing back. First thought I had was that the needle deflection (when you are sewing on domestic the needle is not being moved side to side so stays in straight line, with long arm you are deflecting that needle) is usually more of a problem when moving R to L. This is because of the way the thread comes off the bobbin. It also usually means you need to slow down when going R to L to avoid thread shreds/breaks and get even stitches.
Not picking up bobbin thread--this sometimes happens to me when I don't have the thread in bobbin correctly--either coming the wrong way off the bobbin or because it's just not settle in the bobbin tension arm and has slipped loose. I'd suggest you take out bobbin and rethread. If still a problem with not picking up bobbin thread, move machine to side of quilt, pull out bobbin and unthread needle. Now lean down and with a flashlight slowly rotate the hand wheel to lower needle. Is it coming down so that the hole is mostly visible underneath? is the bobbin pickup mechanism rotating like it should? Now re--insert the bobbin with thread and thread the top and do that again--is the top thread picking up the bobbin thread or does it miss the bobbin pickup? Can't imagine this would happen without warning. I'm not familiar with the Q21 but sure that they have either some videos or maybe a FB group with tech advice. Hope these ideas help some. Also if you keep having problems post up pictures of both the top and bottom of quilted area so we can see better (assuming you are able to get it to pick up the bobbin thread!)
Last edited by quiltingshorttimer; 01-28-2021 at 08:41 PM.