I have a dual monitor system running Windows 10 v. 1903. Sometimes when I put the computer into standby, I will hear at some later time some Windows sounds and when I wake it up, I will find that the (locked) taskbar along with other apps I had opened on one monitor (secondary) are all showing on the other (primary). Occasionally they can be located partially off-screen, so it's impossible to reach the title bar to move them. Even if I unlock the taskbar, I can't drag it back to the original monitor. If I move all the apps to the other monitor I am now able to drag the taskbar. I've checked the monitor cable connections and they seem fine. What else could be doing this, especially when the computer is in standby?

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Update: Not certain anymore what needs to be done to be able to drag the taskbar back to the original monitor. I'm finding that dragging the taskbar seems to be hit or miss even under normal circumstances. Sometimes I can drag it; other times not. Regardless of that, the relocation of the taskbar and all open apps to the primary monitor continues to occur during standby.