So if I rob a jewelery store, and offersome piece of crap as a 'here, use this in the meantime' offering, that would be OK as well? Your logic escapes me . . . Demand return, and sue for damages. They clearly know how to make this right, but won't. Were there no fix, you could drive it indefinitely. Clearly there is no fix at this time, and a botched attempt does not change the situation . . . they just do it later, as has been the case all along, when they have it right. In the meantime, they are obligated to revert the car to original, known functional condition.
(And considering that a botched fix was not addressed in the settlement, I can't fathom that the court would prohibit a back out of the partial until they get it right, and *this* is the point that needs to be pressed with the court . . .)