PSU faulty or overheating issue?

My PS4 is turning off after about 15 minutes into playing games or slightly more when listening to music. It turns off without any warning with several relay clicking sounds, no beeping, no red light. The console may be restarted after reconnecting the power cord or waiting a little and first pressing the eject button (3 beeps, no disc inside) and the power button after (only pressing the power button will give a beep, but nothing happens). When restarted, it performs the corrupted data check.

After opening the PS4 case to replace the termal paste and remove small dust accumulations, the PS4 was started upside down with the bottom plate removed to see if the fan was working properly. It was and the PS4 was running smoothly for the time of testing (45-60 minutes). After closing the case again the problem reoccured.

The PS4 is 2013 model and placed in a well ventilated area with no dust or animal hair around.

Any thoughts on this issue? Thanks a lot!