The stitch balance only works with stitches that have forward/backwards movements.

If you keep the machine just as it is, and sew on a regular cotton fabric, it should be just fine. I see this all the time. The finer the fabric, the straighter the line.

I agree with changing the needle, removing the bobbin, and totally rethreading the machine. I would even shut it off and start again on a scrap of fabric. My old machine usually corrects itself with this method. Do need the pro servicing occasionally too. I take it in at about 2 yr. intervals. Good luck! Not a good time to be without your sewing machine.

I am quite certain it isn't the fabric causing the problem....I have sewn with this weight of fabric frequently and no issues. I did a bit of playing around and under closer examination while sewing, I can actually see the entire needle/shank assembly jump to the right. It is almost as if something isn't quite tight enough in there. Headed to the sewing machine repairman with a sample this morning to see if he can help me without a service call right now.

Let us know what the doctor has to say about the patient!! :) I have that same machine and I like to hear about other people's experiences. I have never had trouble but my day may be coming :)

I just had to purchase a new bobbin case this summer for my 6600 as I had worn it out... will be curious to know what your repairman has to say after examining your machine.

Have you tried stitching on a different fabric.....if that is straight, then you have the wrong needle for your thread/fabric.

You could be right great eyes. You can see at the cut edge the grain is not straight.

Stopped by repairman with the scrap to show him....he said to take off the walking foot and try with a regular foot and if that didn't work to bring it in.....I did and it didn't.....so today I have to take her in.....and like I said earlier, it had nothing to do with the fabric (I didn't pay $1500 for a machine that can't sewn a straight seam through quilting cotton!)

Could this be a very long zig zag? Since there is a pattern to the "jog" you might try resetting the stitch length and style and also the cleaning, etc. that yngldy suggested. I wouldn't take it to the dealer yet as I think this can be remedied if you reset everything. Give that a try and please let us know the result. I have a Brother and they are very similar if not basically the same and often resetting works.

I have a BL....and recently was doing a blanket stitch, and suddenly it went crazy...took it in after trying all I could do....and it went crazier for the dealer...she had to call someone via phone and was told some secret..she went on the screen into the brain of the computer...punched some formula...started it....it stitched some strange circle by itself...then she picked a stitch on screen and perfect!!!!!! Had something to do with internal settings that only the techies can fix!!!!!! Maybe yours did the same...