It was noted that the GAMBIT flights through the first half of 1964 had been mostly successful, but a string of malfunctions occurred starting in the second half of the year and continuing through the first half of 1965. These included the two above-mentioned launch failures plus GAMBIT 4013 which did not return any imagery and GAMBIT 4014 which suffered a battery explosion. GAMBIT 4019 did not return any imagery either. Eventually, it was determined that the culprit was an extra structure added to the SLC-4W umbilical tower that sent resonant vibration through the Atlas-Agena stack at liftoff, jarring random components in the booster and/or spacecraft loose.