selenium log for cannot focus element error

cannotfocuselement.log

12:32:01.593 INFO - Executing: [find elements: By.cssSelector: input[name=Quantity]])
12:32:01.605 INFO - Done: [find elements: By.cssSelector: input[name=Quantity]]
12:32:01.608 INFO - Executing: [clear: 65 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]]])
12:32:01.608 INFO - Executing: [clear: 64 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]]])
12:32:01.628 INFO - Done: [clear: 65 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]]]
12:32:01.631 INFO - Executing: [send keys: 65 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]], [2]])
12:32:01.654 INFO - Done: [clear: 64 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]]]
12:32:01.656 INFO - Executing: [send keys: 64 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]], [2]])
12:32:01.684 INFO - Done: [send keys: 65 [[ChromeDriver: chrome on MAC (1441b6e4cebce511b25c96f261d2cebf)] -> css selector: input[name=Quantity]], [2]]
12:32:02.470 WARN - Exception thrown
org.openqa.selenium.WebDriverException: unknown error: cannot focus element
  (Session info: chrome=49.0.2623.112)
  (Driver info: chromedriver=2.21.371459 (36d3d07f660ff2bc1bf28a75d1cdabed0983e7c4),platform=Mac OS X 10.10.5 x86_64) (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 33 milliseconds
Build info: version: '2.53.0', revision: '35ae25b', time: '2016-03-15 17:00:58'
System info: host: 'DW3931USBUM.local', ip: '10.200.13.235', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.10.5', java.version: '1.8.0_45'
Driver info: org.openqa.selenium.chrome.ChromeDriver
Capabilities [{applicationCacheEnabled=false, rotatable=false, mobileEmulationEnabled=false, chrome={chromedriverVersion=2.21.371459 (36d3d07f660ff2bc1bf28a75d1cdabed0983e7c4), userDataDir=/var/folders/8q/jnq5ys_j7b59c89vlx5w_qg0680g27/T/.org.chromium.Chromium.nIXJqa}, takesHeapSnapshot=true, databaseEnabled=false, handlesAlerts=true, hasTouchScreen=false, version=49.0.2623.112, platform=MAC, browserConnectionEnabled=false, nativeEvents=true, acceptSslCerts=true, locationContextEnabled=true, webStorageEnabled=true, browserName=chrome, takesScreenshot=true, javascriptEnabled=true, cssSelectorsEnabled=true}]
Session ID: 1441b6e4cebce511b25c96f261d2cebf
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
	at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:206)
	at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:158)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:678)
	at org.openqa.selenium.remote.RemoteWebElement.execute(RemoteWebElement.java:327)
	at org.openqa.selenium.remote.RemoteWebElement.sendKeys(RemoteWebElement.java:122)
	at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at org.openqa.selenium.support.events.EventFiringWebDriver$EventFiringWebElement$1.invoke(EventFiringWebDriver.java:335)
	at com.sun.proxy.$Proxy2.sendKeys(Unknown Source)
	at org.openqa.selenium.support.events.EventFiringWebDriver$EventFiringWebElement.sendKeys(EventFiringWebDriver.java:358)
	at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at org.openqa.selenium.remote.server.KnownElements$1.invoke(KnownElements.java:64)
	at com.sun.proxy.$Proxy3.sendKeys(Unknown Source)
	at org.openqa.selenium.remote.server.handler.SendKeys.call(SendKeys.java:50)
	at org.openqa.selenium.remote.server.handler.SendKeys.call(SendKeys.java:1)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at org.openqa.selenium.remote.server.DefaultSession$1.run(DefaultSession.java:176)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)