If the StepOnePlus machine uses flood lamp illumination and you are using ROX to correct for uneven illumination and unequal mastermix loading, in theory, ROX should straighten things out for you.

But, why rely on theory when you can opt to play a pipet like a classical pianist and load all tubes as exactly as possible.

Weigh water with every pipet adjustment to prove what the pipet is delivering beforehand, and then proceed to pipet a fine concerto of perfectly-loaded tube strips.

I probably shouldn't say this next part... but here goes:

I once loaded a plate with a faulty pipet (terriblly uneven wells) but ran the plate anyway - and was absolutely surprised to find that ROX straightened it all out. The results were reasonable and almost perfect...