When it happens, is it reproducible? Meaning, if you delete the 'fake' functions/methods and delete the body of the newly added method and try again, does it generate the 'fake' methods again?
If yes, is it persistent even after restarting the IDE?
If the answer is yes, again, then you might be able to debug it in TCodeCompletionCodeTool.CreateMissingClassProcBodies unit CodeCompletionTool. There is a define VerboseCreateMissingClassProcBodies that might help.