U3419W, Auto Select is Off, still auto switching?

This U3419W keeps reverting to auto switching devices even though Menu- Input Source- Auto Select is set to Off. It also picks my MacBook Pro over my Windows 10 workstation, which is highly annoying considering it switches whenever it wants to. I have updated both systems to use the latest display driver and DDM (Dell Display Manager) versions, but it has not fixed the issue. Any and all help is appreciated as this is highly annoying and distracting. Sometimes, I have to fight with it, constantly resetting the U3419W to HDMI 1 from USB Type-C until it gives in -- at least until it doesn't anymore. I'm pretty much at my wit's end. If I manually set the input, I expect the U3419W to stay with that input until I set a different one. I had to switch to manual in the first place because it would never pick my Windows machine. U3419W is using the latest firmware, M3B107.