I don't know the specifics of your monitor. But you say the source is in power-save mode? I think then it has also signaled to the monitor to enter power-save m

I don't know the specifics of your monitor. But you say the source is in power-save mode? I think then it has also signaled to the monitor to enter power-save mode. So if your monitor supports it, turn off energy-saving mode settings might fix the issue. It might also be less annoying to wait 4 seconds, if you think of it as helping to save the planet ;-)