Some of those "12v" leds are exactly that - designed for 12.0v, or maybe 12.6v (battery voltage). Problem is, an RV (or car) 12v system operates between 13.3v and 14.8v much of the time, and some of those leds have insufficient power regulation to handle it. Most leds makers (in China) have learned that by now, but some bad examples still turn up from time to time.
Leds are very voltage sensitive (they actually run at around 2v), so a bit of over or under voltage drives them nuts.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC