I think most modern cars are so voltage-sensitive, whenever a friend tells me that he is having some sort of intermittant problem, I suspect bad contacts. Even the side marker bulbs were a non-issue, in my opinion. All you had to do was clean the contacts and reassemble with some dielectric grease, and they work perfectly thereafter. I noticed that Volvo's engineers used three grounding straps on my wife's 1999 V70, so they were careful in that respect.