Appium stops exactly after three testscripts

I am not able to run more than three scripts in the appium

Version : Appium :1.4.8
Mac: 10.9.4

Attached logs for details
info: [debug] Unzip successful

info: [debug] Got a relaxed match for app in zip, be careful for app match errors

info: [debug] Using locally extracted app: /var/folders/66/hfpq649s1gv92ww7dzj19tbm0000gp/T/1151017-1579-yjzow2/Payload/LA-iPad.app

info: [debug] Creating new appium session ad005fa4-afb9-4145-9efd-20e71ee0ab50

error: Unhandled error: TypeError: Cannot read property ‘args’ of null
at [object Object].Appium.invoke (/Applications/Appium.app/Contents/Resources/node_modules/appium/lib/appium.js:259:18)
at [object Object]. (/Applications/Appium.app/Contents/Resources/node_modules/appium/lib/appium.js:124:14)
at [object Object]. (/Applications/Appium.app/Contents/Resources/node_modules/appium/lib/devices/ios/ios.js:193:5)
at [object Object]. (/Applications/Appium.app/Contents/Resources/node_modules/appium/lib/devices/device.js:95:7)
at [object Object]. (/Applications/Appium.app/Contents/Resources/node_modules/appium/lib/devices/device.js:172:7)
at /Applications/Appium.app/Contents/Resources/node_modules/appium/lib/helpers.js:143:13
at /Applications/Appium.app/Contents/Resources/node_modules/appium/lib/helpers.js:70:13
at ChildProcess.exithandler (child_process.js:742:7)
at ChildProcess.emit (events.js:110:17)
at maybeClose (child_process.js:1015:16)
at Socket. (child_process.js:1183:11)
at Socket.emit (events.js:107:17)
at Pipe.close (net.js:485:12) context: [POST /wd/hub/session {“desiredCapabilities”:{“app”:"/Users/lnmobiletesting/Documents/workspace/LA-Native/Utilities/LA-iPad.ipa",“deviceName”:“iPhone”,“platformName”:“iOS”,“udid”:“5ba8583a4047fecaa2dd4319bd0d86b7a49bd842”}]