You should be able to step through modules just like any other functions you want to step through. It is possible that if there was an error in the module it would fail to cache the module when it is loaded into the context. I've not come across this error before however, so if you come across it again please let us know so we can try reproduce it.
over 4 years ago
it is strange. now it works. is there any criteria to make debug enabled? what i did is adding argument to my event. then stepin worked for module.