As I stated, I recognized some of the actors and cross-referenced the movies they are in to get to films made between 1975-1976. The back cover art of one of the VHS tapes showed the dinner scene and an IMDB comment by a fan emphasized that in Europe the actor names were changed into French and German stage names. By 1980 Clair started directing. I think she's most noted for the Cheerleaders movie.
This one is a hard movie to locate and define because it was done on purpose. An American movie for the European market. 1976. Clair Dia under the table and one male actor is Tyler Reynolds. Cross-link the participants and you will get the title. Like most porn, everyone is trying to hide who they are.
The full movie