Screen sharing multiple screens has issues in El Capitan

I have some very interesting info to report on this exact problem. This is a complicated description so I hope you can follow. The new piece of info comes at the end.

I have been troubleshooting this issue on my Mac Pro 5,1 2010 all day long. It was helpful to see that designating a different screen as the main screen "solved" the problem, except that meant my screens (3 of them - a 24 inch Dell, a 24 inch Samsung, and a 20 inch Samsung) were not in the configuration I wanted them to be in. My Dell had been the main screen with the 24 inch Samsung on a shelf right above it and the 20 inch Samsung to the left of the 24 inch dell. However I very purposely had all 3 screens arranged horizontally in System Prefs because I didn't like trying to click on menus (File, Edit, etc) at the top of my main screen and accidentally ending up with the mouse up on the Samsung on the shelf above because I moved too quickly. So I pretended the 24 inch Samsung was to the left of my 20 inch Samsung -- it meant having to move my mouse all the way to the left to get to it instead of up, but was worth the tradeoff. However in this configuration, I found out that screen control only worked on 1 screen at a time from any other computer.

So this thread caused me to try (without physically moving anything yet) to make my 24 inch Samsung on the top shelf the main screen, and voila -- screen sharing across all 3 screens from other computers started working again. So I figured it was something about the brand of screen itself and meant that I needed to physically take apart my system and put the Samsung on the bottom shelf and the Dell on the top but leave the 20 inch Samsung where it was on the left. So I did all that and, of course, had to re-configure the display arrangement so my computer knew where everything was again -- and Screen Sharing was NOT working again after all of that moving things around!

Long story short, I realized that it wasn't which screen was designated as the "main" screen that causes this bug. It was the arrangement layout itself!! I played around with it and if I went back to telling the computer that my main 24 inch screen was in front of me, 20 inch screen was to the left of that, and my 2nd 24 inch screen was directly above my main 24 inch screen, screen sharing worked just fine from other computers!! I never had to physically swap the Samsung and the Dell in the first place! I just had to NOT use a side-by-side completely horizontal arrangement configuration. Which, unfortunately, means I once again have to deal with it being too easy to accidentally end up with my cursor on the top screen -- but at least I know what the heck was causing it now.

Definitely a bug and I experience this in Yosemite and Sierra but NOT Mavericks. So it started in Yosemite.

Hope this finding at least helps others.

And no, I do not want to put my top screen to the right of my main screen. I have something else there.

Temporary Fix:

Had to drag my main screen to be the far left screen in Display Preferences.

Instructions:

- System Preferences

- Displays

- Arrangement

- Click and drag the screens so that the one with the gray title bar is on the left.

Only seem to have this problem with 3+ screens. 2 screens still works fine.

I have mbp retina i7 at work with 3 screens. I can confirm it's only a bug with 3 monitors. Unplugging either of the external monitors released the mouse for remote control on the remaining two (one of which will be the laptop itself of course).

Yes - I see the same issue. Screen sharing a MacBook Pro with two additional monitors used to work perfectly. I could select which display to 'view' and control with the pull-down. Immediately after El Capitan, I can connect to the host machine fine, and see/select each of the displays fine, but the mouse clicks are not applied correctly. Seems the clicks go to a different display than the one viewed/controlled. When I click in the controlled display, the active app goes to the background, and I see the menubar go blue. I can watch the click behavior (such as a right click) actually show up on a different display than the location of the pointer.

I'm running a Mac Pro (Early 2009) and El Capitan 10.11.1 with 8 30" cinema monitors configured as one large screen. (4 across X 2 high) with the control monitor (the one with the menu bar) at the bottom of column 3. In screen sharing mode from a remote mac in the same office it appears the mouse clicks are not registering. However, moving the mouse on the multi-screen system shows the mouse cursor is several screens over.

If I put the multi-screen machine into mirror mode (8 screens all showing the single control screen) then I can control the multi-screen Mac remotely. Mouse clicks work as expected.

I hope Apple OS developers will look into this. It was working fine before El Capitan.

+1

I solved the issue by designate the left most screen as "main screen" (in System Preferences->Displays drag the little "menu bar" to the left screen).

Apple, definitely, should resolve this bug.

Still a problem! In my case we are running Yosemite (due to 3rd party software compatibility/stability issues) on the target Mac while using El Capitan on the source Mac.

Still an issue as of 10.11.6. I think maybe the only solution is to buy the full version.😠 But has anyone actually made sure it works there?

I'm connecting to a Mac Pro with 3 Thunderbolt displays from a retina MacBook Pro. You would think that if they go to the trouble of putting in an option to display each screen separately they would make sure each screen is actually controllable. This is either really lazy programming or really lame quality control.

I also have this problem, with 10.11.6. Running 3.4 GHz core i7 iMac with 32 GB ram. May have to disconnect external displays when logging off at end of day 😟

This solution worked for me as well. Thank you.