Same issue here, I have a 2 x 2 monitor setup, horizontally they're fine but vertically I can't have anything maximised in the bottom screens as it will bleed onto the taskbars of the top screens.
My suspicion is the Settings app for adjusting the monitor layouts. Most of the new Settings screens are pretty janky and this seems to lack the finesse needed to put the screens exactly where they need to be; spacing between monitors is inconsistent; it's just (another) terrible UI.
However, I seem to have found a fix...
The NVIDIA Control Panel also has the option to Set up multiple displays and simply moving them about and putting them back where they were with that and applying the change appears to have solved the issue, now to see how long it sticks for.