My MicroPro 3000 recently started exhibiting a weird issue. It works completely fine if set to be always on.

However when setting it to a power mode which turns itself off automatically it stops working very quickly. Same issue can be replicated by turning the power button to off or simply unplugging the power cable.

When doing that it just starts thumping (with or without any power plugged in) for ~15 seconds and turns off. Then I need to wait about 5 minutes before it starts working again.

Unfortunately it's out of warranty so I can't send it in for repair. Any idea what the problem might be or how much it would cost to repair it?