Mac Pro Late 2013 display behaving erratically

Hi samonell,

Thanks for using Apple Support Communities.

I see that you are having an issue with your Mac Pro's display when using specific apps. Thank you for the screenshot. I definitely wouldn't want that happening to my Mac. Let's see how I can help with this issue.

First, I would recommend starting your computer in safe mode, and testing to see if you get the same result. Safe mode (sometimes called safe boot) is a way to start up your Mac so that it performs certain checks, and prevents some software from automatically loading or opening. Please use the following article to start into safe mode:

OS X El Capitan: Start up in safe mode

If you have the same issue in safe mode, then I would recommend creating a new user and testing again. Testing in a new user can isolate the issue you are currently having from the main user, to the entire system. Use OS X El Capitan: Set up users on your Mac, specifically, this section:

Add a user

1. Choose Apple menu > System Preferences, then click Users & Groups.

2. Click the lock icon to unlock it, then enter an administrator name and password.

3. Click the Add button below the list of users.

4. Click the New Account pop-up menu, then choose a type of user.

   
   

   Administrator: An administrator can add and manage other users, install apps, and change settings. The new user you create when you first set up your Mac is an administrator. Your Mac can have multiple administrators. You can create new ones, and convert standard users to administrators. Don’t set up automatic login for an administrator. If you do, someone could simply restart your Mac and gain access with administrator privileges. To keep your Mac secure, don’t share administrator names and passwords.

Best Regards.

Hello Samonell,

Thank you for trying those steps. We have a couple of other things for you to try.

First, please make sure that you have a current backup of your Mac's important data. We recommending backing up with Time Machine using an external hard drive. The following article will help you make a backup:

Use Time Machine to back up or restore your Mac

Once you've backed up data, please use How to reinstall OS X to erase your hard disk using Disk Utility, and reinstall a fresh copy of OS X, specifically, this section:

If you're reinstalling for other reasons

1. Start up from OS X Recovery by holding Command-R immediately after turning on or restarting your Mac. Release the keys when you see the Apple logo. Startup is complete when you see the OS X Utilities window.
   
2. If you do want to erase your disk before reinstalling OS X, open Disk Utility from the OS X Utilities window, then use Disk Utility to erase the disk. Quit Disk Utility when done.
   Erasing the disk isn't necessary unless you're transferring your Mac to a new owner, partitioning your disk for use with Boot Camp, or attempting to resolve an issue that Disk Utility can't repair.
   
3. Choose Reinstall OS X from the OS X Utilities window, then follow the onscreen instructions.
   This installs the latest version of OS X that was previously installed on your Mac.

This can help isolate the issue from software to hardware. Once you've reinstalled OS X, test and see if you get the same result.

Cheers.

Greetings Samonell,

Thank you for also trying those steps.

Since you are still having this issue, we would like to get you in contact with Apple Support. Please use the following link:

Contact Apple Support

Best Regards.