Input field crashes on Android 4.1.2 (Unity 5.1.1f1)

Everything works fine if running standalone on PC: can perform any actions with Input fields. The situation remains the same when running on Android and device is in landscape mode, which makes any text edit to take place in separated fullscreen window.

However, if editing with default keyboard in portrait mode OR with custom keyboard which does not bring up that fullscreen edit window (so, in both these variants game stays visible, along with keyboard) strange issue appears: if during edit the cursor was moved at least once, the game will crash on the end of editing, after all functions in End Edit (string) were successfuly called.

I have tried disabling any consequent events of editing a field, no results.

What is wrong with that Input field? Thank you in advance.

EDIT: Tried creating absolutely blank game consisting only of one Input field. No results.

EDIT2: Found out that game will not crash in the following scenario: 1)edit Input field, still not moving the text cursor 2)clicking OK 3)clicking Input field again, as to start another edit 4)entered earlier text will all be selected (as if Ctrl+A in PC) 5)clicking somewhere in the text will place the edit cursor there, now allowing to edit and not crashing on pushing OK in the end.(having cursor moved mannualy still crashes on OK press, though)

EDIT3: Found out that not having the cursor moved causes the crash, but the ability to see dat blue thing:

Still can't fix this...

EDIT4: Done some more testing. Two Samsung Galaxy S3 minis with Android 4.1.2 with different life history both crash on these conditions, however, Samsung Galaxy S5 did not. It appears the problem may be model specific, and not platform specific...

No progress on the Samsung, however.

EDIT5: Managed to get error log:

java.lang.Error: FATAL EXCEPTION [main] Unity version : 5.1.1f1 Device model : samsung GT-I8190N Device fingerprint: samsung/goldennfcxx/golden:4.1.2/JZO54K/I8190NXXAMA1:user/release-keys Caused by: java.lang.IndexOutOfBoundsException: charAt: -1 < 0 at android.text.SpannableStringBuilder.charAt(SpannableStringBuilder.java:112) at android.text.Selection.setSelection(Selection.java:81) at android.text.Selection.setSelection(Selection.java:115) at android.widget.Editor$InsertionHandleView.updateSelection(Editor.java:3783) at android.widget.Editor$HandleView.positionAtCursorOffset(Editor.java:3501) at android.widget.Editor$HandleView.updatePosition(Editor.java:3528) at android.widget.Editor$PositionListener.onPreDraw(Editor.java:2335) at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:707) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1944) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1113) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4481) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725) at android.view.Choreographer.doCallbacks(Choreographer.java:555) at android.view.Choreographer.doFrame(Choreographer.java:525) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711) at android.os.Handler.handleCallback(Handler.java:615) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4856) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774) at dalvik.system.NativeStart.main(Native Method)

Got no idea on what is going on...