Another sample of "GAMBARA-NAI(NOT to GAMBARU)" singer(s) are "Puffy".
When Puffy made debut in USA, their concept of "GAMBARA-NAI" was not accepted in USA. With some another effort, Puffy made some degree of success (I don't know in detail) but this is an example Japanese production did not understand why "GAMBARA-NAI" was not accepted in foreign country.