My P15 doesn't go in stand-by

I have a P15 and I noticed a problem in the last couple of weeks.
When I finish my listening session and I want to switch of my system, I push the power bottom on the remote control or on the front panel but I don’t hear the rumour of the relè that detach the power: the display becomes dark but the output plugs remain operative.
In this case, the only way to shut down the unit is to power off the main switch on the back panel.
This happens not all the time but in the last two weeks it happened at least 3 times and I wonder if I’m facing some problem in my P15?
Did you experience the same problem?

I have all my outlets in the “Always On” mode so I don’t know about your problem but have you tried to make a “Restore Defaults” to see if that fix it for you?

Yes, I also tried to factory restore but sometimes it happens as well.
I have my outlets on switched mode.