S2417DG, switching input HDMI to DP not working

I bought this S2417DG a few years ago and it's been working fine. I'm very happy with it overall. The warranty expires on May 12, 2020. I have my desktop computer connected via the DP port and I've had no problems.

Not long ago, I purchased a SNES classic and connected it via the HDMI input. I have no issues with this set up at all.

The problem I'm having is that sometimes when I want to switch from the HDMI input back to the DP input, I can't. I use the options menu on the monitor to change sources, and I never have any problems switching *to* the HDMI mode. But often when I try to switch back the screen stays black (although obviously on, I can see the backlighting) and then after a few seconds the message about power saving comes up and nothing further happens. I make sure to wake up my computer a few seconds before trying to switch, and still have this issue. Sometimes switching back and forth between inputs seems to do the trick but often this is not the case, especially if I have something still running (eg the input is still putting out a picture) on the HDMI input.

I'm hoping that there is an easy fix or something simple that I'm overlooking. I would like to sometimes be able to use my computer, switch over to play a game, pause, switch back to check something, switch back to the game, etc. Anyone else have this problem?