The important thing is: it must always only one of the connected devices turned on. Standby is not enough here, as this usually still light is sent to the optical output of the device.
So connect both devices. One completely off, then comes the other.
Once I need the second device, before I turn one off (so that both are off) and only then the second device on.
If you do that so it funktoniert without problems.
Maybe should some who rashly give bad reviews, to deal a little more accurate with some things.