When I let my laptop go idle, the P2415Q turns off with a message "Entering Power Save Mode.". After roughly every 25s, the P2415Q turns itself on, displays the same message and turns off. This repeats indefinitely. All this is accompanied by a very subtle coil whine which starts whining just a few seconds before it turns on. It's especially noticeable when the P2415Q transitions from off state, when it is completely silent, to the message and it's very annoying.
This happens on three laptops, one of them is brand new Dell XPS 13 and second is company laptop HP ProBook. The P2415Q is connected via mDP port. All machines have Windows 10 Pro. Dell XPS 13 uses USB Type-C to DP dongle. HP has its own DP port.