Tips shouldn't be sparking to much if you aren't using nickel plated metal. Then it will spark a lot.
You can try cleaning with alcohol. It will remove the non-conducting oil as well as smoke (coal / carbon) that will populate the tips after a while.
What thickness are you using and what power levels? I think I only used 100J around for 0,3mm pure nickel and for 0,2 50J-->80J but to my knowledge after experience even those power levels I used was way too high!
So pulling down the power to when the nickel fastens correctly is something you need to learn and go from there.
I don't think "ONE" lipo can do 1200 amps+... but I may be wrong so in a sense that may be an easy answer to a tricky problem here.
Is the kweld newly build? I have had a ONE nut lose on it on the copper bar row and it acted weird. Also ONE time it has been a little lose on the positive or negative INPUT or if it was OUTPUT. It is sure worth a double check here. Be careful not to short or drop metal into the kweld, allthough mine survived a short once I don't expect luck to be on my side always.
