As painful as separation is you must not accept the car back until the problem has been resolved.
This includes when you get the car back if the problem resurfaces you immediately take the car back and drop it off.
If you accept the car with the problem unresolved you tell the dealer you will accept the car with the problem unresolved. The dealer will not be as enthusiastic pursuing a solution.
There is another thing to consider. If one accepts the car back with the CEL on and believes this to be not be important, if another problem surfaces that also would trigger a CEL one doesn't know this. Problems can stack up.
Some cars have a real problem with turning on the CEL for no good reason. I do not think your Cayman is one of these. The problem is the owner ignores the CEL and continues to drive the car and other problems accumulate until at some point there are symptoms that prompt the owner to take the car in. It is at this point the owner learns there are several expensive to address problems and decides to dispose of the car vs. addressing the problems.