Most full screen Applications or games steal focus from the desktop so that there is no click through or interference with the task bar, requiring you to alt tab or physically click the window to shift mouse/keyboard focus.
So any application on the primary computer in full screen that takes focus duplicates any and all left, right or scroll movements on the primary computer when on a secondary screen. I am not sure how I can state this any more clearly.
I am also using windows 11. I run no xmouse third party tool, and I have checked windows 11 settings to ensure there is no xmouse like feature enabled on the primary or on any of the secondaries. My secondaries are also running windows 10. Maybe that is part of the issue.
I did run the other version in the EQ thread that was mentioned, but it did not fix the issue, and I reverted to the supported release rather than run a beta that you chose to lock a thread on rather than address issues others were still having.
If you want clips of the actions I can capture for you.
Lets say I have world of warcraft on the primary in full screen. The scroll on the mouse there zooms your view in and out.
I use multiplicity and move to one of the secondary computers, open a web browser, do a search and as I scroll my WoW display is zooming as i scroll the webpage on the secondary.
If I right mouse click something on the secondary computer and hold, it swings my character around. If I press both mouse buttons at the same time on the secondary it makes my character run off a cliff on the primary.
In lightroom in full screen. Same thing on the secondary. In Elden ring, same thing....etc etc
if I bind a key do disable mouse movement completely in a game before I move to a secondary this lets me get around this. But that defeats the purpose of the software.
This is in seamless mode with a four computer set up
Standard computer configuration.
Show multiplicity in the task bar is the only thing checked in settings.
Control switching based on mouse movement, no options are checked
Show status window when controlling another computer is on and works, as well as darkens screen.
Show a colored line on the computer with focus never changes to the secondary and blinks off and on the primary.