Flywheel won't turn forward

Manual Page 13, item 16 is the clutch wheel that releases and re-engages the drive to the needle.

https://www.bernina.com/en-CA/SupportData/Out-of-Print/BERNINA_730_731_732_manual

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See page 72 how to avoid machine trouble of this manual
BERNINA_730_731_732_manual

I suspect Bernina of America is less than helpful about the replacement of such a part but you can try contacting them. Likewise, I don't see such parts listed at https://www.sewingpartsonline.com/bernina-730-sewing-machine-parts.aspx?sort.ss_cat_sort=desc&index=1

You might try https://www.a1sewingmachine.com/bernina-sewing-machine-parts.htm

That said, you might try contacting the following gentleman who has specialized in Berina parts for 25 years. See the contact link on the following page: https://www.ebay.com/i/223984261952?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=223984261952&targetid=4580634169192455&device=c&mktype=&googleloc=&poi=&campaignid=395665111&mkgroupid=1232552744834023&rlsatarget=pla-4580634169192455&abcId=1129776&merchantid=51291&msclkid=f59df6824f571d5a441da87ae3dabbd7

Try turning the flywheel while activating the lower/raise feed dogs switch. There is a gear lock on the inside of the flywheel, while some machines have a automatic switch that works when the bobbin winder post is moved to the off position.
Cheers,
Embroidery Services
San Diego, CA

What exactly do you mean? The knob that raises and lowers the feet? If so, I suggest you look at it carefully..even take a magnifing glass to it. There may be thread, or something else stuck in there.If so, try to catch it with tweezers..carefully! Also make SURE your machine is unplugged! If this isn't it..I would have to suggest taking it to your dealer.

try these links

BERNINA artista 730 Support BERNINA


Bernina 730 Record Parts


Bernina 730 Sewing Machine Cleaning oiling and Maintenance

The thread sensor eye is probably dirty.

Try removing your hook, if it becomes free, you might a piece of needle in your hook race! If that doesn't work, you need to take a Bernina dealer for service.