Remote Access Problems using Two Displays

I have an iMac Retina running Mac 10.10.5 Yosemite. I have been accessing the desktop via Apple Remote Desktop or VNC without ever having a problem.

I attached a second display via thunderbolt cable (which worked perfectly as soon as it was connected). I did find that remote access using either Apple Remote Desktop or VNC was at first spotty and now is non-existent.

Anybody have any experience with this?

I use Teamviewer 11.x for mac. Works fine with 2 monitors.

I use remote desktop to connect to some customers, some of them have 2 displays and I did not notice any trouble
I am on 10.9.5
I connect to other customers using teamviewer and I find it far more difficult to connect (must retry always 1 or more)

I am having significant issues with Apple Remote Desktop ever since I added a second display. If I turn off Remote Management and then turn it on and I find the screen loads then immediately loses connection. After that I can’t connect at all.

Not sure why, but the problem has gotten much worse lately. Previously, I was able to connect and would get this confused black screen constantly getting larger and smaller (as if it was trying to figure out whether to open one screen or two). I would have to force quit Apple Remote Desktop and then try again and it would work. Lately, however, I can’t connect at all.

I have not updated anything. The computer with two displays is running 10.10.5.

The computers logging in have various versions of Mac OS (from 10.9.5 to 10.11.5) and Apple Remote Desktop.

I also can’t log in using screen sharing either.

You really ought to ask this question on Apple’s forums.

I use ARD here for accessing the computers around our house, including two others that have multiple screens. I’ve never had trouble accessing them.

Now that said, you could be simply running into a limitation of the shared computer. It could be that there’s not t enough processing power to generate and send two screens worth of data.

Will do. Thanks.

Not sure if this was the problem, but things seem to be working better now.

I noticed the ports that had to be forwarded to my Mac’s ip address. Some of the ports were set as both TCP/UDP but I was reading that they should be set only to TCP because it was more reliable. I corrected this problem and have not noticed a problem since.