I pulled out the Power Supply board and the Analog board and did a quick ESR check. Three caps were a bit high, but still within the tolerance window, but I replaced them anyway. Currently I don't really have much replacement caps, and all of them were quality Nichicon-chemicon brand, which usually don't need replacement.

The problem persists, but I found out that when the machine is cool, the sleep and restart work fine, but after about 15 minutes when the machine warms up, it will start to act up this way. With the bad caps, the problems are usually reversed. I would say that there is somewhere a bad transistor..