Either way, I've witnessed welders, especially new guys, switch to one polarity or the other just because they thought that is what it was supposed to be without checking the manufacturer's specs/recommendations.
They have been running innershield only and the shop has them run gas shielded and they automatically switch the polarity when it didn't need to be.
All kinds of possibilities, point is to check and see how it is recommended to be run and make sure that is how it is set up at the machine. After all, it is possible the machine is set to negative but it is supposed to be positive.
Also, the nickel electrodes are a little difficult for some guys. Check all your parameters and then experiment with technique.
Have a Great Day, Brent