Any way to see runtime error of a shader on Android?

I spent a day debugging by trial and error a shader, which was displaying correctly in editor and on several Android devices, but displaying incorrectly on one specific Android device. It was NOT a compile error, i.e. no pink rectangles, just displaying incorrectly, as if parts of the shader code wasn't running.

The culprit turned out to be code in the following format:

Code (Shader):

1. if ( ... )
2.     return ...
3. else
4.     return ...

The problem was returning directly from within the if statement. Simply changing the code to:

Code (Shader):

1. fixed4 foo;
2. if ( ... )
3.     foo = ...
4. else
5.     foo = ...
6. return foo;

fixed the problem, i.e. creating a variable and returning after the if/else, rather than returning from within the if/else directly.

My question is: was there any way to debug this kind of problem by seeing some error logged somewhere? (I don't see anything in the adb logcat output, but I haven't examined every one of hundreds of lines of log output.)

Also, anyone know why this problem can occur on some Android devices but not others, and not in Editor?