appium: Clear sometimes fails

https://github.com/appium/appium/issues/3367 /cc @boulevardaed

@boulevardaed
I'm using v1.2.2 (REV cf6ff5939ddc6b4d45fcbabfbfe13c950e0058c4). Here's what I found now:

Test case:
two edittexts. The first contains hinted words: "email", the second contains hinted words: "url", with pre-filled text www.123.com.
I need to input "123@456.com" in the first edittext and add /456 into the second one.

My code:
edittext1.sendKeys("123@456.com");
edittext2.clear();
edittext2.sendKeys("www.123.com/456");

Current result:
The first line: email123@456.com
The second line: blank with hinted text: url

Log of clear() part:
info: --> POST /wd/hub/session/7205a5d5-c130-4426-9d0c-8a6e845f2516/element/4/clear {"id":"4"}
info: [debug] Pushing command to appium work queue: ["element:clear",{"elementId":"4"}]
info: [debug] [BOOTSTRAP] [debug] Got data from client: {"cmd":"action","action":"element:clear","params":{"elementId":"4"}}
info: [debug] [BOOTSTRAP] [debug] Got command of type ACTION
info: [debug] [BOOTSTRAP] [debug] Got command action: clear
info: [debug] [BOOTSTRAP] [debug] Updating class "class com.android.uiautomator.core.UiDevice" to enable field "mUiAutomationBridge"
info: [debug] [BOOTSTRAP] [debug] Updating class "class com.android.uiautomator.core.UiAutomatorBridge" to enable field "mInteractionController"
info: [debug] [BOOTSTRAP] [debug] Updating class "class com.android.uiautomator.core.UiDevice" to enable field "mUiAutomationBridge"
info: [debug] [BOOTSTRAP] [debug] Updating class "class com.android.uiautomator.core.UiAutomatorBridge" to enable field "mInteractionController"
info: [debug] [BOOTSTRAP] [debug] Finding methods on class: class com.android.uiautomator.core.InteractionController
info: [debug] [BOOTSTRAP] [debug] Finding methods on class: class com.android.uiautomator.core.InteractionController
info: [debug] [BOOTSTRAP] [debug] Finding methods on class: class com.android.uiautomator.core.InteractionController
info: [debug] [BOOTSTRAP] [debug] Clearing text not successful using selectAllDelete now trying to send delete keys.
info: [debug] [BOOTSTRAP] [debug] Finding methods on class: class com.android.uiautomator.core.UiAutomatorBridge
info: [debug] [BOOTSTRAP] [debug] Clearing text not successful falling back to UiAutomator method clear
info: [debug] [BOOTSTRAP] [debug] Returning result: {"value":"Clear text not successful.","status":13}
info: [debug] Responding to client with error: {"status":13,"value":{"message":"An unknown server-side error occurred while processing the command.","origValue":"Clear text not successful."},"sessionId":"7205a5d5-c130-4426-9d0c-8a6e845f2516"}
info: <-- POST /wd/hub/session/7205a5d5-c130-4426-9d0c-8a6e845f2516/element/4/clear 500 16616.424 ms - 195

I know it's hard to fix after so many tries.. Thanks for your effort.