Mine is a stock unmodified gt4, bought new, transmission replaced at 9k miles, now with 21k miles, approx 25 track events. Recently, after a 3 d drive thru Cherohola Skyway, Tail of the Dragon, Wolf Pen Gap, and the surrounding beautiful mountain roads, I experienced a few instances in which I couldn't engage third gear, and then there was a loud metallic grind into 4th. This only happened after several days of hard-driving, and not when driven casually. It then happened again, finding a pocket of space to put some speed down, off an exit ramp off the highway, after sitting in terrible Atlanta traffic. Each time, the car has been hot, and engine and oil temps are up but not dangerously high. I took it to the dealer, they kept it for 10-12days, and were unable to replicate, and basically inspected it, drove it, and said there's nothing they can do because they couldn't replicate it, and the transmission, synchros and clutch were all operating within "factory specifications" Transmission fluid looked normal as well. I drove it home, as hard as I could, and the issue hasn't happened since. I'm annoyed and upset, as I have a few track days planned for December, but any advice as to how to proceed with the dealer, or what this may be a sign of?