Lady Diana

Check with your State to see if they have a lemon law.....apply that argument to the second machine and demand a refund.Tell them that if they are not going to refund, you will be contacting the Attorney General Office and local media about not taking back a defective out of the box machine!
If this right out of the box issues, the dealer should take it back refund your money and apologize. They, in turn, need to send it back since it is new. They are loosing nothing by refunding your money on this machine since it is inferior and they will send it back to Juki. Then sell your first machine if it is fixed. I would also talk to Juki about your first machine and, of course, mention the second one as well. I would look at the comparable Janome machine. I have numerous Janome machines and have never had a single one in the shop. Best wishes on a quick resolve. BTW if you purchased your first machine on sale, then they should honor your purchase price on the second on sales as well. I'm sure you will have to pay for the difference. They are used to selling far below MSRP. All dealers do.