Instruments is crashing one one iphone while on the other one it works great

Strangely the tests work on one device but not the other!
i am using 2 iphone5 devices, both running ios 8.1.
for some reason the first iphone works perfectly while one the other the application is installed but not get launched.
according the log it seems that the instruments is crashed!
any idea what am i missing here? i tried to compare the configuration on both devices & it seems identical (enable ui automation is set to true).
any help will be most appreciated…

DesiredCapabilities capabilities = new DesiredCapabilities();
	capabilities.setCapability("deviceName", "Automation test2");
	capabilities.setCapability("device", "iPhone 5");
	capabilities.setCapability("udid", "8a81fe38953a66ae654563bbd8ca87d7339a939d");
	capabilities.setCapability(CapabilityType.VERSION, "8.1");
	capabilities.setCapability(CapabilityType.PLATFORM, "Mac"); 
	 capabilities.setCapability("platformName", "iOS");
    capabilities.setCapability("app", "/Users/qa/Desktop/Appium/");

driver = new AppiumDriver(new URL(“”), capabilities);

4-11-10 13:03:13:883 - info: [debug] Starting command proxy.

2014-11-10 13:03:13:884 - info: [debug] Instruments socket server started at /tmp/instruments_sock
2014-11-10 13:03:13:884 - info: [debug] Starting instruments

2014-11-10 13:03:13:896 - info: [debug] Instruments is at: /Applications/
2014-11-10 13:03:13:896 - info: Launching instruments
2014-11-10 13:03:13:897 - info: [debug] Attempting to run app on real device with UDID 8a81fe38953a66ae654563bbd8ca87d7339a939d
2014-11-10 13:03:13:897 - info: [debug] Spawning instruments with command: /Applications/ -t /Applications/ -D /tmp/appium-instruments/instrumentscli0.trace -w 8a81fe38953a66ae654563bbd8ca87d7339a939d com.cloudengines.pogoplug -e UIASCRIPT “/Users/qa/Library/Application Support/appium/bootstrap/bootstrap-60f23230385b0cfa.js” -e UIARESULTSPATH /tmp/appium-instruments
2014-11-10 13:03:13:897 - info: [debug] And extra without-delay env: {}
2014-11-10 13:03:13:897 - info: [debug] And launch timeouts (in ms): {“global”:90000}

2014-11-10 13:03:14:997 - info: [debug] [INSTSERVER] Instruments exited with code 253

2014-11-10 13:03:14:997 - info: [debug] Killall instruments

2014-11-10 13:03:15:001 - info: [debug] Instruments crashed on startup
2014-11-10 13:03:15:001 - info: [debug] Attempting to retry launching instruments, this is retry #1
2014-11-10 13:03:15:001 - info: [debug] Killall iOS Simulator

2014-11-10 13:03:20:003 - info: Launching instruments

Yes i do agree with that, even for me on some iOS devices, Instruments are crashing. And for other devices it works fine.
Also i face this issue, that tests is running fine on one machine and on other machine instruments are crashing.

If the problem is with Instruments.Then try and open instruments on your Mac and check if you are able to launch your application through Instruments->Automation ,as Appium internally uses Instruments to automate. It might help you get to the root cause.