When I updated Xcode from 6.4 to 7.2 my Appium UI Automation stopped working, with instruments crashing.
Appium: 1.4.13
Xcode: 7.2
Here are the error
Making sure you have Use Native Instruments Library checked under Advance settings for IOS platform in Appium's UI and ensuring Enable UI Automation setting in setting--developer helps as mentioned in the comments.
Use Native Instruments Library
Enable UI Automation