@elk yinzer where was the buckle sitting on your boot? Close to the metal eye on the spur, on top of your boot, pulled closer to the shank of the spur? Also, did you have the strap double wrapped around the shank of the spur?
I have the buckle centered over my boot. I tied a knot in the webbing that won't fit through the metal eye on the spur so it give me something to cinch down tight against. I don't double wrap it.