The problems with PPP
It all sounds quite logical but teachers who use this method will soon identify problems with it:
Students can give the impression that they are comfortable with the new language as they are producing it accurately in the class. Often though a few lessons later, students will either not be able to produce the language correctly or even won't produce it at all.
Students will often produce the language but overuse the target structure so that it sounds completely unnatural.
Students may not produce the target language during the free practice stage because they find they are able to use existing language resources to complete the task.