Immediately what comes to mind is that Porsche switched from the GT1 engine blocks used (and still used) for years in professional 911 racing subjecting the motors to the rigors of Motorsport. This new block used in the direct injected motors which is shared with the other 911 models has not seen the same levels of stress testing or mileage. It is a cost saving measure to share these blocks among models and that is why the GT3 switched to it. Not to mention the efficiency and emissions benefits that direct injection brings with the newer motors but the decision is mostly due to cost saving among platforms.
The cars could be sidelined for months as Porsche figures out what exactly is going on. Owners should not drive their cars and certainly should do any high performance driving events.
A Porsche spokesperson had this to say about the matter: "Identifying the issue is one thing, but undergoing comprehensive testing to ensure the remedy has solved the problem is another. And it depends on what the remedy is; if it is an electronic software issue then it is much easier to implement than a mechanical component of the engine, especially given the GT3 is essentially a race engine. The thresholds in that engine are lot higher for performance but the tolerances are much lower, and given we are an engineering company that prides itself on the reputation we are not going to take any risks.
The default setting would be to wait a little while longer to make sure we do the job to 110 percent then we will do that as opposed to rush something and cross our fingers; that is not the way we do things. Amazingly, our customers are quite understanding as they know we are an engineering company and they know we won't make any compromises so they are prepared to be patient because they know then they cars will be indestructible. Has it been ideal for the company, far from it - the GT3 is the halo car of the company. Our customers are disappointed, sure, but they understand it is in good hands and they know it will be permanent and it will be great."
Porsche will resolve this. However, one does have to question if saving money by sharing blocks will now turn out to cost Porsche much more money in recalls and new parts than if they just used the tried and true block they are still racing with today.