Hello Dadeacon!!!
Cleanliness is JOB ONE!!! If your components are'nt clean or they have a thin film of residue on them then, that's where your problem begins!!! However, it does'nt end there...
You're saying that you're experiencing crater cracks? If this is the case then, you should start to lower your current when you're just short of the end of the weld but, not too much because, you want to deposit metal at the end, then come back into the weld from the end or the crater of the weld about 1/4" to 3/8", not depositing metal, and at the same time, lowering your current (Foot Pedal) until the arc extinguishes itself, and Keep the torch there until you're finished with the post flow of shielding gas!!!
DO NOT LIFT OR REMOVE THE TORCH BEFORE YOUR POST FLOW CYCLE OF GAS SHIELDING IS FINISHED!!! How do you have your shielding gas and backpurge configured?? Are you using post flow? Also, make sure that your tungsten is the right one and that it's not contaminated at ALL!!! What is your back purge flow rate or setting on?
ALSO!!! Do'nt change your travel angle on your torch when you do the crater fill because, if you do, then the crater will NOT be shielded when you're travelling back into the weld!!!
Always fill the crater during your restarts, and make sure you're watching how fluid the puddle is because, you DO'NT need to have so much current once the puddle has been established in order to deposit filler metal!!! The flipside of the coin is not to have enough current whereby there is'nt enough "wetting action" at the toes for good fusion there...
I also noticed that you're getting indications on the toes of the fillet?
Are you oscillating the weld pool? Please let me know when you get time!!!
Respectfully,
SSBN727 Run Silent... Run Deep!!!