Screen-Sharing / VNC connection freezing

Background:

Since updating to OS X El Capitan 10.11.5, you may experience random Screen-Sharing or VNC connection freezes. The freezing issue is difficult to reproduce in any consistently reliable way, but one thing that tends to be commonplace is that Safari or Google Chrome is in use when the freezes occur, often viewing web video or a site with embedded video or animated content in some form. It also can happen when using any of GPU intensive apps like Apple Maps, Launchpad or Dashboard. This is mostly related to the lack of Hardware accelerated 3D graphics which are unfortunately not available to OS X virtual machines (a know limitation since many years). Hopefully this will change with upcoming OS X versions from Apple.

What to do when a remote connection freeze happens:

1. Login to Customer Portal with your credentials provided with the Welcome-Email
2. In the "Instance" list click on Action > Open Console
3. Within the Console click anywhere in the screen-area to unlock the freeze
4. After a few seconds, your remote connection session should be back again or you should be able to reestablish a new connection.

Workaround for Safari related freezes:

1. From the Safari browser, close any existing windows
2. Now pull down the Safari menu and choose "Preferences"
3. Go to the "Security" tab
4. Completely disable WebGL by unchecking the box next to "Allow WebGL"
5. Close Preferences in Safari, then quit and relaunch Safari

Workaround for Google Chrome related freezes:

1. From the Chrome browser, close any existing windows
2. Now pull down the Safari menu and choose "Preferences"
3. In the "Settings" tab scroll down and click on "Show advanced settings"
4. Scroll down to "System" and disable WebGL by unchecking the box next to "Use hardware acceleration when available"
5. Quit and relaunch Chrome

A side note:

This issue seems also to affect many other Mac users using real Mac hardware. Here is one of many public articles about this OS X issue.