Make sure your project build settings are generating a dSYM file. DEBUG_INFORMATION_FORMAT should be set to dwarf-with-dsym for all configurations
The below solution worked for me ,i hope it will help you.
Goto build setting of your project then Search for debug information format in build setting and search for "Debug information format" then set "Debug information format" to "DWARF with dSYM file"
and make sure Generate debug symbol in build setting is set to Yes.
Check for true "run script only when installing" on Run Script
Elaborating Bruno's response, if you already have a script phase that you need to run all the time, create a new dedicated phase in order to avoid conflicts.