Airbus, you are correct on the donut and sleeves.

If your engine is only 6 months old, I would be hitting up Tower for a repair. Magnum had some issue with valve springs a while back and I know Hobby People was good about stepping up to the problem. They would fix it or send you the parts, your choice. I would expect Tower to do likewise. It may well be worth a call to their customer service.

Don