iOS Crash on call to EtceteraBinding.showAlertWithTitleMessageAndButtons from OnGUI

I get a crash in my iOS program on line

 EtceteraBinding.showAlertWithTitleMessageAndButtons( "" , "Blablbabla" , new string [] {  "Cancel" ,  "Restore"  } );

in OnGUI method. I found this by placing Debug.Log("...") before and after this line.

Xcode stops on line 73 in CrashReporter.mm, with message in green "EXC_BREAKPOINT code=EXC_ARM_BREAKPOINT ...."

In my C# code I have

 Action<string> restoreHandler = null;
 restoreHandler = (string title) => {
               EtceteraManager.alertButtonClickedEvent -= restoreHandler;
 ....
 };
 EtceteraManager.alertButtonClickedEvent += restoreHandler;

before call to EtceteraBinding.showAlertWithTitleMessageAndButtons

The crash occurs frequently, but not always.

I think I have latest version of plugin. I update it recently.

How should I fix this?