Those numbers are not surprising. As just a mere sales/marketing type person, I used to carry a handful of gaskets in my 'ditty bag" for the truck half tank coupler. About 4-5 times a year, when I was able to work my way into the "back rooms", I would run across a leaky coupler gasket & fix it for the customer no matter the brand. About 1/2 the time the account would remember this & we would pick up plus business - service, parts, rental, truck sales, etc. from new accounts.
And yes, I was coached in proper procedures by a "factory trained" service professional. That plus my growing up on a Michigan farm learning to fix machinery in the middle of a field in pouring rain , knee deep in mud & a formal education in auto engineering at WMU allowed me to muddle my way through this procedure.