Thanks for all your input. I am happy to report that the R772 that is connected to the 5 Vol. controls is working fine after my "right hand man" tracked out all the feed lines to the volume controls (running under the house in a dark crawl space) and found 2 staples that were going thru the 4 conductor and not around it! After removal of the staples the unit is reported as playing fine for 4 days straight.
Being human we all make mistakes. Staying profitable in this business means keeping your mistakes to a minimum!