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It looks to me like the 2 pieces were not at the same temperature. The smaller piece was at the correct temperature as can be seen by the flowing of the solder but the larger piece wasn't. It's best to start heating the larger piece away from the joint and then work the heat toward the smaller piece. The question is did the solder wick into the joint from the first attempt? If not then it needs to be taken apart and redone. There should always be a tiny gap between the two pieces for the solder to flow into. gbritnell