You have mentioned that working with thin aluminum parts is easy because it has melting temp.500 degrees less then that of aluminum. What is the exact temp.? This seems soldering and not brazing. At 5.50 video time, you are inserting a screw. Immediately on insertion the molten metal looses the surface tension. If it is forming a proper alloy then this should not be the case. Although I am critical about your product the bond strength is good. Is it SnZn combination? There is lack of fluidity, maybe using flux can sort it out.