I normally measure the tip when they are hot. The tip is likely Micro-arcing inside. We have the same trouble with all our tips when pulse welding. How many amps is the Tokin torch and cable rated for?
A new Tregaskiss tip is .048”. They eventually have to be changed due to the micro-arc but it takes a lot of welding.
I would try a .052” tip and see if it makes a difference.
Let me know if you need any help.