If you and the joint owner of the car are struggling to make the payments, it is best to work together to find a solution. This may involve contacting the lender to see if you can make a payment plan or refinance the loan, or selling the car and using the proceeds to pay off the loan.
It is also important to communicate with the joint owner about the situation and make sure you are both on the same page. If you are unable to reach an agreement, you may need to consider legal action to protect your interests.
Letting a car be repossessed should only be considered as a last resort, as it can have serious and long-lasting consequences for both joint owners.